More filename shenanigans

yt/subscribe.pl

@@ -467,9 +467,12 @@ FETCH_LOOP: foreach my $id (keys(%{$videos})) {
 					next FETCH_LOOP;
 				}
 				# Sometimes the downloader lies about file extensions
-				if (!-s $file && $file =~ /\.webm$/i) {
+				if (!-s $file) {
 					$file =~ s/\.webm$/.mp4/;
 				}
+				if (!-s $file) {
+					$file =~ s/\.mp4$/.webm/;
+				}
 				# But we still need *a* file
 				if (!-s $file) {
 					warn('No output video file: ' . $NAME . '/' . $file . "\n");