avformat/avidec: Fix memleak with dv in avi

Found-by: 连一汉 <lianyihan@360.cn>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit b98dafe045)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/avidec.c

@@ -608,6 +608,7 @@ static int avi_read_header(AVFormatContext *s)
                 if (s->streams[0]->info)
                     av_freep(&s->streams[0]->info->duration_error);
                 av_freep(&s->streams[0]->info);
+                av_freep(&s->streams[0]->internal);
                 av_freep(&s->streams[0]);
                 s->nb_streams = 0;
                 if (CONFIG_DV_DEMUXER) {