Fix Null pointer expection when Phone is in low memory

ThumbnailManager tries to get the bitmap and throws null
pointer exception when cache is null.

Change-Id: Iba557e5d9aa6c0990ee47c79788c4c1c55121c63
CRs-Fixed: 539366
Merge "Fix Null pointer expection when Phone is in low memory"
Mms: zh-rTW translations

Change-Id: I0898b751460249c434d9178279cd7335bf3d5500
Merge remote-tracking branch 'cm/cm-10.2' into qcril
Merge remote-tracking branch 'origin/qcril' into caf
Merge remote-tracking branch 'caf/jb_mr2' into caf