demux_lavf: clear sticky avio EOF in drop_buffers

A stream can report a one-shot EOF and then continue producing data
(disc-nav jump boundaries). Also clear a sticky read error, the
underlying source is being reused.

demux/demux_lavf.c

@@ -1805,6 +1805,9 @@ static void demux_drop_buffers_lavf(demuxer_t *demuxer)
     stream_drop_buffers(priv->stream);
     avio_flush(priv->avfc->pb);
     avformat_flush(priv->avfc);
+    // Clear sticky EOF/error to reuse this demuxer.
+    priv->avfc->pb->eof_reached = 0;
+    priv->avfc->pb->error = 0;
     reset_dovi_split_state(demuxer);
 }