fix on error reporting

frontend-js/src/main/js/GuiConnector.js

@@ -106,7 +106,7 @@ GuiConnector.updateMouseCoordinates = function(x, y) {
 };
 
 GuiConnector.alert = function(error) {
-  var self = this;
+  var self = GuiConnector;
   logger.error(error);
   if (self._errorDialog === undefined) {
     self._errorDialog = document.createElement("div");