thumbnail: Disabled seeking in live streams (quick fix)

thumbnail.c

@@ -76,6 +76,7 @@ int main(int argc, char *argv[])
 		job_failed("Writing temporary file failed: %s", av_err2str(err));
 
 	/* Create thumbnail */
+	if (!jlookup(argv[4], "srcurl"))
 		av_seek_frame(demux, -1, (2L*demux->duration)/5L, 0);
 	memset(&pkt, 0, sizeof(pkt));
 	av_init_packet(&pkt);