Overrides EditorUi defining beforeunload handler

war/js/diagramly/ElectronApp.js

@@ -610,4 +610,6 @@ FeedbackDialog.feedbackUrl = 'https://log.draw.io/email';
         	}));
 		}
 	};
-})();
+	
+	EditorUi.prototype.addBeforeUnloadListener = function() {};
+})();