libavformat/mov: Replace duplicate stream_nb check by assert

Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -2438,8 +2438,7 @@ int ff_mov_read_stsd_entries(MOVContext *c, AVIOContext *pb, int entries)
     MOVStreamContext *sc;
     int pseudo_stream_id;
 
-    if (c->fc->nb_streams < 1)
-        return 0;
+    av_assert0 (c->fc->nb_streams >= 1);
     st = c->fc->streams[c->fc->nb_streams-1];
     sc = st->priv_data;