parsing error when missing channel in frequency line

I got the following error when calling Cell.all('wlan0'):
Traceback (most recent call last):
  File "a.py", line 2, in <module>
    print Cell.all('wlan0')
  File "/usr/local/lib/python2.7/dist-packages/wifi/scan.py", line 34, in all
    cells = map(Cell.from_string, cells_re.split(iwlist_scan)[1:])
  File "/usr/local/lib/python2.7/dist-packages/wifi/scan.py", line 44, in from_string
    return normalize(cell_string)
  File "/usr/local/lib/python2.7/dist-packages/wifi/scan.py", line 138, in normalize
    frequency, channel = frequency_re.search(value).groups()
AttributeError: 'NoneType' object has no attribute 'groups'

Here is the output of iwlist wlan0 scan
wlan0     Scan completed :
          Cell 01 - Address: 58:6D:8F:2B:DA:8E
                    Channel:149
                    Frequency:5.745 GHz
                    Quality=65/70  Signal level=-45 dBm  
                    Encryption key:on
                    ESSID:"3408TT"
                    Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 18 Mb/s; 24 Mb/s
                              36 Mb/s; 48 Mb/s; 54 Mb/s
                    Mode:Master
                    Extra:tsf=0000000edea58e3a
                    Extra: Last beacon: 140ms ago
                    IE: Unknown: 0006333430385454
                    IE: Unknown: 01088C129824B048606C
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: 2D1AEE081AFFFF000001000000000000000000000000000000000000
                    IE: Unknown: 3D16950D0000000000000000000000000000000000000000
                    IE: Unknown: DD090010180200F02C0000
                    IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00
          Cell 02 - Address: C8:3A:35:F8:05:C0
                    Channel:11
                    Frequency:2.462 GHz (Channel 11)
                    Quality=38/70  Signal level=-72 dBm  
                    Encryption key:on
                    ESSID:"ruanruan"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 9 Mb/s
                              18 Mb/s; 36 Mb/s; 54 Mb/s
                    Bit Rates:6 Mb/s; 12 Mb/s; 24 Mb/s; 48 Mb/s
                    Mode:Master
                    Extra:tsf=000002f32927a101
                    Extra: Last beacon: 4880ms ago
                    IE: Unknown: 00087275616E7275616E
                    IE: Unknown: 010882848B961224486C
                    IE: Unknown: 03010B
                    IE: Unknown: 2A0104
                    IE: Unknown: 32040C183060
                    IE: Unknown: 2D1A6E1117FF000000010000000000000000000000000C0000000000
                    IE: Unknown: 3D160B070600000000000000000000000000000000000000
                    IE: Unknown: 3E0100
                    IE: WPA Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: DD180050F2020101030003A4000027A4000042435E0062322F00
                    IE: Unknown: 0B05010012127A
                    IE: Unknown: 4A0E14000A002C01C800140005001900
                    IE: Unknown: DD07000C4304000000
                    IE: Unknown: 0706434E20010D10
          Cell 03 - Address: CC:34:29:FB:DB:68
                    Channel:11
                    Frequency:2.462 GHz (Channel 11)
                    Quality=43/70  Signal level=-67 dBm  
                    Encryption key:on
                    ESSID:"lizzy"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
                              9 Mb/s; 12 Mb/s; 18 Mb/s
                    Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
                    Mode:Master
                    Extra:tsf=0000000134e62194
                    Extra: Last beacon: 5108ms ago
                    IE: Unknown: 00056C697A7A79
                    IE: Unknown: 010882848B960C121824
                    IE: Unknown: 03010B
                    IE: Unknown: 2A0100
                    IE: Unknown: 32043048606C
                    IE: Unknown: 2D1A6E1003FF00000000000000000000000000000000000000000000
                    IE: Unknown: 3D160B071100000000000000000000000000000000000000
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: WPA Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: DD180050F2020101000003A4000027A4000042435E0062322F00
                    IE: Unknown: DD05000AEB0100
                    IE: Unknown: DD960050F204104A0001101044000102103B0001031047001000000000000010000000CC3429FBDB681021000754502D4C494E4B10230009544C2D57523734304E1024000B352E302F362E302F372E3010420007312E312E302E331054000800060050F204000110110018576972656C657373204E20526F757465722057523734304E100800022288103C0001011049000600372A000120
          Cell 04 - Address: BC:F6:85:9F:60:51
                    Channel:11
                    Frequency:2.462 GHz (Channel 11)
                    Quality=22/70  Signal level=-88 dBm  
                    Encryption key:on
                    ESSID:"D-Link_DIR-600M"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
                              24 Mb/s; 36 Mb/s; 54 Mb/s
                    Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s
                    Mode:Master
                    Extra:tsf=000000010afebff5
                    Extra: Last beacon: 5284ms ago
                    IE: Unknown: 000F442D4C696E6B5F4449522D3630304D
                    IE: Unknown: 010882840B162430486C
                    IE: Unknown: 03010B
                    IE: Unknown: 2A0100
                    IE: Unknown: 2F0100
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (1) : TKIP
                        Authentication Suites (1) : PSK
                    IE: Unknown: 32040C121860
                    IE: Unknown: 2D1A6C181BFF00000000000000000000000000000000000000000000
                    IE: Unknown: 3D160B001300000000000000000000000000000000000000
                    IE: Unknown: DD090010180207F0050000
                    IE: WPA Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (1) : TKIP
                        Authentication Suites (1) : PSK
                    IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00
                    IE: Unknown: DD1E00904C336C181BFF00000000000000000000000000000000000000000000
                    IE: Unknown: DD1A00904C340B001300000000000000000000000000000000000000
          Cell 05 - Address: C8:D3:A3:31:12:8C
                    Channel:1
                    Frequency:2.412 GHz (Channel 1)
                    Quality=33/70  Signal level=-77 dBm  
                    Encryption key:on
                    ESSID:"dlink"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
                              9 Mb/s; 12 Mb/s; 18 Mb/s
                    Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
                    Mode:Master
                    Extra:tsf=000000f054ee8f63
                    Extra: Last beacon: 5756ms ago
                    IE: Unknown: 0005646C696E6B
                    IE: Unknown: 010882848B960C121824
                    IE: Unknown: 030101
                    IE: Unknown: 2A0100
                    IE: Unknown: 32043048606C
                    IE: Unknown: 2D1A6E181EFF00000000000000000000000000000000000000000000
                    IE: Unknown: 3D1601051100000000000000000000000000000000000000
                    IE: WPA Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : TKIP CCMP
                        Authentication Suites (1) : PSK
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (2) : TKIP CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00
                    IE: Unknown: DD8A0050F204104A0001101044000102103B0001031047001063041253101920061228C8D3A331128C1021000E442D4C696E6B2053797374656D73102300084449522D3630304C102400084449522D3630304C1042000D32303037303431332D303030311054000800060050F2040001101100084449522D3630304C1008000226881049000600372A000120
                    IE: Unknown: DD1E00904C336E181EFF00000000000000000000000000000000000000000000
                    IE: Unknown: DD1A00904C3401051100000000000000000000000000000000000000
                    IE: Unknown: DD0600E04C020160
          Cell 06 - Address: 58:6D:8F:2B:DA:8D
                    Channel:6
                    Frequency:2.437 GHz (Channel 6)
                    Quality=65/70  Signal level=-45 dBm  
                    Encryption key:on
                    ESSID:"3408DD"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
                              24 Mb/s; 36 Mb/s; 54 Mb/s
                    Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s
                    Mode:Master
                    Extra:tsf=0000000ede5ae6ce
                    Extra: Last beacon: 5356ms ago
                    IE: Unknown: 0006333430384444
                    IE: Unknown: 010882848B962430486C
                    IE: Unknown: 030106
                    IE: Unknown: 2A0100
                    IE: Unknown: 2F0100
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: 32040C121860
                    IE: Unknown: 2D1AEE181BFFFF000001000000000000000000000000000000000000
                    IE: Unknown: 3D16060F0400000000000000000000000000000000000000
                    IE: Unknown: DD090010180204F02C0000
                    IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00
          Cell 07 - Address: EC:88:8F:70:4A:D2
                    Channel:6
                    Frequency:2.437 GHz (Channel 6)
                    Quality=21/70  Signal level=-89 dBm  
                    Encryption key:on
                    ESSID:"TP-LINK_xlfc"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
                              9 Mb/s; 12 Mb/s; 18 Mb/s
                    Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
                    Mode:Master
                    Extra:tsf=000000020a8359d7
                    Extra: Last beacon: 5540ms ago
                    IE: Unknown: 000C54502D4C494E4B5F786C6663
                    IE: Unknown: 010882848B960C121824
                    IE: Unknown: 030106
                    IE: Unknown: 0706555320010D14
                    IE: Unknown: 2A0100
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: 32043048606C
                    IE: Unknown: 2D1A6E1003FFFF000000000000000000000000000000000000000000
                    IE: Unknown: 331A6E1003FFFF000000000000000000000000000000000000000000
                    IE: Unknown: 3D1606051500000000000000000000000000000000000000
                    IE: Unknown: 341606051500000000000000000000000000000000000000
                    IE: WPA Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: DD180050F2020101030003A4000027A4000042435E0062322F00
                    IE: Unknown: DD0900037F01010000FF7F
                    IE: Unknown: DD800050F204104A0001101044000102103B0001031047001000000000000010000000EC888F704AD21021000754502D4C494E4B10230009544C2D57523834314E10240003312E3010420003312E301054000800060050F204000110110018576972656C657373204E20526F757465722057523834314E100800020086103C000101
          Cell 08 - Address: 20:DC:E6:DF:8A:A2
                    Channel:6
                    Frequency:2.437 GHz (Channel 6)
                    Quality=16/70  Signal level=-94 dBm  
                    Encryption key:on
                    ESSID:"TP-LINK_DF8AA2"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
                              9 Mb/s; 12 Mb/s; 18 Mb/s
                    Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
                    Mode:Master
                    Extra:tsf=00000314e0c3d3e5
                    Extra: Last beacon: 5536ms ago
                    IE: Unknown: 000E54502D4C494E4B5F444638414132
                    IE: Unknown: 010882848B960C121824
                    IE: Unknown: 030106
                    IE: Unknown: 050400010000
                    IE: Unknown: 0706555320010D14
                    IE: Unknown: 200100
                    IE: Unknown: 2A0100
                    IE: IEEE 802.11i/WPA2 Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: 32043048606C
                    IE: Unknown: 2D1A6E1003FFFF000000000000000000000000000000000000000000
                    IE: Unknown: 3D1606051100000000000000000000000000000000000000
                    IE: WPA Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: DD180050F2020101030003A4000027A4000042435E0062322F00
                    IE: Unknown: DD0900037F01010000FF7F
                    IE: Unknown: DD0E0050F204104A0001101044000102
          Cell 09 - Address: C8:3A:35:58:8B:08
                    Channel:8
                    Frequency:2.447 GHz (Channel 8)
                    Quality=18/70  Signal level=-92 dBm  
                    Encryption key:on
                    ESSID:"Tenda_588B08"
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
                              24 Mb/s; 36 Mb/s; 54 Mb/s
                    Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s
                    Mode:Master
                    Extra:tsf=00000180aeb15183
                    Extra: Last beacon: 5336ms ago
                    IE: Unknown: 000C54656E64615F353838423038
                    IE: Unknown: 010882840B162430486C
                    IE: Unknown: 030108
                    IE: Unknown: 050401030000
                    IE: Unknown: 2A0100
                    IE: Unknown: 2F0100
                    IE: Unknown: 32040C121860
                    IE: Unknown: 2D1AFE181BFFFF000001000000000000000000000000000000000000
                    IE: Unknown: 3D16080F0000000000000000000000000000000000000000
                    IE: Unknown: DD090010180200F02C0000
                    IE: WPA Version 1
                        Group Cipher : CCMP
                        Pairwise Ciphers (1) : CCMP
                        Authentication Suites (1) : PSK
                    IE: Unknown: DD180050F2020101000003A4000027A4000042435E0062322F00


As you can see, there is one line like this:
Frequency:5.745 GHz
So the "frequency_re" doesn't work for it.