processing dialog cannot be closed manually

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

@@ -133,7 +133,7 @@ GuiConnector.showProcessing = function(messageText) {
       width : "150px",
       closeOnEscape : false,
       open : function(event, ui) {
-        $(".ui-dialog-titlebar-close", ui).hide();
+        $(".ui-dialog-titlebar-close", ui.dialog | ui).hide();
       },
     });
   }