Fix ERROR_MALFORMED return in bool method, BetterSniffMPEG4

There's possibility that ERROR_MALFORMED is returned from
bool method, BetterSniffMPEG4 in MPEG4Extractor.
The bug is from 452599f23a36207d436f7275ebc7e3ccac6ca76c.

This commit solves such a minor coding bug.

Bug: 67665041
Test: boot and play video

Change-Id: I7cf2002143983370d6ee50ce12c3b81069b8564b
1 file changed