Some code does call av_free_packet() on failed av_new_packets(), this
prevents the freeing of uninitialized pointers.
Originally committed as revision 20801 to svn://svn.ffmpeg.org/ffmpeg/trunk
AVPacket structure now resides also.
Patch by Thilo Borgmann thilo.borgmann googlemail com, see the mailinglist
thread "Google Summer of Code participation" for additional discussion.
Originally committed as revision 18353 to svn://svn.ffmpeg.org/ffmpeg/trunk