TYPO3 Core

IE8 produces an Error when not running in compatibility mode, and someone tries to rightclick on a page.

1. login to the backend
2. go into page view
3. right click on a page in the tree

ie8 script debugger info:

/**
 * switch function that either makes an AJAX call
 * or loads the request in the top frame
 *
  * @param    params    parameters added to the URL
 * @return    nothing
     */ 
    callURL: function(params) {    
        if (this.ajax && Ajax.getTransport()) { // run with AJAX
            params += '&ajax=1';
            new Ajax.Request(this.clickURL, {
                method: 'get',
                parameters: params,
                onComplete: function(xhr) {
                    var response = xhr.responseXML;
                    if (!response.getElementsByTagName('data')[0]) return;
                    var menu  = response.getElementsByTagName('data')[0].getElementsByTagName('clickmenu')[0];
                    var data  = menu.getElementsByTagName('htmltable')[0].firstChild.data;
                    var level = menu.getElementsByTagName('cmlevel')[0].firstChild.data;
                    this.populateData(data, level);
                }.bind(this)
            });
        } else { // fallback with no AJAX, no isCMLayers
            top.loadTopMenu(this.clickURL + '?' + params);
        }
    },

the line in question:
top.loadTopMenu(this.clickURL + '?' + params);

the error output:
Object doesn't support this property or method

the file in question:
clickmenu.js
(issue imported from #M12070)