avidec : Free codec context before initializing the chained DV demuxer.

Originally committed as revision 24279 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/avidec.c

@@ -397,6 +397,7 @@ static int avi_read_header(AVFormatContext *s, AVFormatParameters *ap)
 
                 ast = s->streams[0]->priv_data;
                 av_freep(&s->streams[0]->codec->extradata);
+                av_freep(&s->streams[0]->codec);
                 av_freep(&s->streams[0]);
                 s->nb_streams = 0;
                 if (CONFIG_DV_DEMUXER) {