Merge: Cover exception by undefined _progressListener rpgtkoolmv#203

rpgtkoolmv#203

Author: Nathan Bolton

js/rpg_core/ProgressWatcher.js

@@ -12,15 +12,15 @@ ProgressWatcher._bitmapListener = function(bitmap){
     this._countLoading++;
     bitmap.addLoadListener(function(){
         this._countLoaded++;
-        this._progressListener(this._countLoaded, this._countLoading);
+        this._progressListener && this._progressListener(this._countLoaded, this._countLoading);
     }.bind(this));
 };
 
 ProgressWatcher._audioListener = function(audio){
     this._countLoading++;
     audio.addLoadListener(function(){
         this._countLoaded++;
-        this._progressListener(this._countLoaded, this._countLoading);
+        this._progressListener && this._progressListener(this._countLoaded, this._countLoading);
     }.bind(this));
 };