avformat/id3v2: Use ffio_ensure_seekback() in id3v2_read_internal()

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/id3v2.c

@@ -1072,6 +1072,8 @@ static void id3v2_read_internal(AVIOContext *pb, AVDictionary **metadata,
             break;
         }
 
+        ret = ffio_ensure_seekback(pb, ID3v2_HEADER_SIZE);
+        if (ret >= 0)
             ret = avio_read(pb, buf, ID3v2_HEADER_SIZE);
         if (ret != ID3v2_HEADER_SIZE) {
             avio_seek(pb, off, SEEK_SET);