fix "list index out of range" error on line 128

Traceback (most recent call last):
  File "ifstop", line 218, in <module>
    if sys.argv[1] == '--help':
IndexError: list index out of range
added sys.argv size check
Merge pull request #1 from KawaiDesu/patch-1

fix "list index out of range" error on line 218