stagefright-plugins: Fix crash if nal size is not 3/4
stagefright-plugins: Fix crash if nal size is not 3/4

IF a media file reported a nal size length not
equals to 3/4. It will asserts.
Change it to report error on that media instead
of asserts.

FEIJ-335

Change-Id: Id46a423102407388eff2b7f3b069cb7c4354df32

AOSPB/external_stagefright-plugins,AOSPB/external_stagefright-plugins