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
MMS: Create an entry in messaging conversation for WAP PUSH

Messaging application displays the SMS/MMS based on
thread id. If WAP PUSH is present in DB but the actual
retrieval of MMS failed then Messaging app would not
show that message and hence user would never get a chance
to manually download that MMS. Hence it is required that
for every WAP PUSH we create thread id in thread table.

CRs-Fixed: 534457
Change-Id: I7e4b16072a8f2cd5d1424cd8b476ddd98cb9fbeb
Merge "MMS: Create an entry in messaging conversation for WAP PUSH"
Merge "Fix Null pointer expection when Phone is in low memory"
Merge remote-tracking branch 'caf/jb_mr2' into caf
Merge remote-tracking branch 'origin/qcril' into caf
Merge remote-tracking branch 'caf/jb_mr2' into caf
Merge remote-tracking branch 'origin/qcril' into caf