Ticket #2923: 2923_3.patch

_source/core/dom/domobject.js

@@ -50 +50 @@
         {
                 return function( domEvent )
                 {
-                        domObject.fire( eventName, new CKEDITOR.dom.event( domEvent ) );
+                        // In FF, when reloading the page with the editor focused, it may
+                        // throw an error because the CKEDITOR global is not anymore
+                        // available. So, we check it here first. (#2923)
+                        if ( window.CKEDITOR )
+                                domObject.fire( eventName, new CKEDITOR.dom.event( domEvent ) );
                 };
         };