cinera_player_pre.js: Fix scoping of "this"

cinera/cinera_player_pre.js

@@ -1238,7 +1238,7 @@ Player.prototype.doFrame = function() {
                     this.platformPlayer.getCurrentTime()
                         .then(function(Result) {
                             Parent.currentTime = Result;
-                    if(this.desiredTime == -1) { this.desiredTime = this.currentTime; }
+                            if(Parent.desiredTime == -1) { Parent.desiredTime = Parent.currentTime; }
                             Parent.updateProgress();
                         });
                 } break;