add a check before find_frame_end call

Patch by Limin Wang % lance P lmwang A gmail P com %
Original thread:
date: 04/09/2007 03:54 PM
subject: [Ffmpeg-devel] [PATCH] fix segment fault in h264_parse if buf_size is zero

Originally committed as revision 8714 to svn://svn.ffmpeg.org/ffmpeg/trunk