playlist_queue: simplify error handler

Return early on error, save one level of indent.

src/playlist_queue.c

@@ -103,16 +103,15 @@ playlist_open_into_queue(const char *uri, struct playlist *dest)
 
 	struct input_stream *is;
 	struct playlist_provider *playlist = playlist_mapper_open(uri, &is);
-	if (playlist != NULL) {
+	if (playlist == NULL)
-		enum playlist_result result =
+		return PLAYLIST_RESULT_NO_SUCH_LIST;
-			playlist_load_into_queue(uri, playlist, dest);
-		playlist_plugin_close(playlist);
 
-		if (is != NULL)
+	enum playlist_result result =
-			input_stream_close(is);
+		playlist_load_into_queue(uri, playlist, dest);
+	playlist_plugin_close(playlist);
 
-		return result;
+	if (is != NULL)
-	}
+		input_stream_close(is);
 
-	return PLAYLIST_RESULT_NO_SUCH_LIST;
+	return result;
 }