M3UParser: check for NULL before setting meta data

Bug:16351654
Change-Id: I64e9510f719b220471522b4d78a9b00a98bda772

Conflicts:
	media/libstagefright/httplive/M3UParser.cpp
Fix Externally reported security issue

bug: 12724697
Change-Id: I57f37dbb3b01c0c3d3256be67c395352dd6ada13