Declared some existing fields in the cnstructor for extra clarity

multiplayer.js

@@ -280,6 +280,12 @@
             // the main playback source at any given time
             this._mainSource = null;
 
+            // the element wrapping the playlist sidebar items
+            this._playlist = null;
+
+            // the playlist title element
+            this._playlistTitle = null;
+
             // list of elements to show/hide based on playlist presence
             this._playlistUI = [];