tta: Check return value of avio_seek and avoid modifying state if it fails

Signed-off-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Justin Ruggles <justin.ruggles@gmail.com>

libavformat/tta.c

@@ -142,9 +142,10 @@ static int tta_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp
     int index = av_index_search_timestamp(st, timestamp, flags);
     if (index < 0)
         return -1;
+    if (avio_seek(s->pb, st->index_entries[index].pos, SEEK_SET) < 0)
+        return -1;
 
     c->currentframe = index;
-    avio_seek(s->pb, st->index_entries[index].pos, SEEK_SET);
 
     return 0;
 }