Do not show alert if another one is already shown

src/mibew/js/source/default/utils.js

@@ -164,12 +164,24 @@
         vex.dialog.buttons.NO.text = Mibew.Localization.trans('Cancel');
     });
 
+    /**
+     * Checks if vex dialog is already opened.
+     * @returns {Boolean}
+     */
+    var isVexOpened = function () {
+        return (vex.getAllVexes().length > 0);
+    }
+
     /**
      * Alerts a message.
      * @param {String} message A message that should be displayed.
      */
     Mibew.Utils.alert = function(message) {
         setVexDefaults();
+        if (isVexOpened()) {
+            // Do not open alert if one already opened.
+            return;
+        }
         vex.dialog.alert({message: message});
     }