avformat/samidec: Fix memleak upon read header failure

The already parsed subtitles (contained in an FFDemuxSubtitlesQueue)
would leak if an error happened upon reading a subsequent subtitle
or when creating extradata.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit f161f8e4ad)
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavformat/samidec.c

@@ -108,6 +108,8 @@ static int sami_read_header(AVFormatContext *s)
     ff_subtitles_queue_finalize(s, &sami->q);
 
 end:
+    if (res < 0)
+        ff_subtitles_queue_clean(&sami->q);
     av_bprint_finalize(&buf, NULL);
     return res;
 }