Merge pull request #273 from gausszhou/master

fix: issues #272

src/litegraph.js

@@ -7477,6 +7477,8 @@ LGraphNode.prototype.executeAction = function(action)
      * @method adjustMouseEvent
      **/
     LGraphCanvas.prototype.adjustMouseEvent = function(e) {
+	var clientX_rel = 0;
+        var clientY_rel = 0;
 	    
     	if (this.canvas) {
             var b = this.canvas.getBoundingClientRect();