Videos aufnehmen können.uc.js nur teilweise Funktion in Fx 126

(function() {

/*    if (location.href !== AppConstants.BROWSER_CHROME_URL) return; */
 if(location.href != 'chrome://browser/content/browser.xhtml') return;
   try {
      CustomizableUI.createWidget({
         id: 'menu-button',
         type: 'custom',
         defaultArea: CustomizableUI.AREA_NAVBAR,
         onBuild: function(aDocument) {
            var button = aDocument.createElementNS('http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul', 'toolbarbutton');
            var attributes = {
               id: 'menu-button',
               class: 'toolbarbutton-1 chromeclass-toolbar-additional',
               removable: 'true',
               label: 'Videos aufnehmen können',
               tooltiptext: Services.prefs.getBoolPref('media.mediasource.enabled') ?
                  'Videos gesperrt' : 'Videos frei',
               oncommand: '(' + onCommand.toString() + ')()'
            };
            for (var a in attributes) {
               button.setAttribute(a, attributes[a]);
            };
            function onCommand() {
               var isEnabled = !Services.prefs.getBoolPref('media.mediasource.enabled');
               Services.prefs.setBoolPref('media.mediasource.enabled', isEnabled);
               event.target.ownerGlobal.BrowserReload();
               var windows = Services.wm.getEnumerator('navigator:browser');
               while (windows.hasMoreElements()) {
                  let button = windows.getNext().document.getElementById('menu-button');
                  if (isEnabled)
                     button.setAttribute('tooltiptext', 'Videos gesperrt')
                  else
                     button.setAttribute('tooltiptext', 'Videos frei');
               };
            };
            return button;
         }
      });
   } catch(e) { };

   if (document.documentElement.hasAttribute('privatebrowsingmode') &&
       !Services.prefs.getBoolPref('media.mediasource.enabled'))
   {
      let button = document.getElementById('menu-button');
      button.click();
      window.addEventListener('unload', function() {
         button.click();
      });
   };

   var css =
      '#menu-button[tooltiptext="Videos gesperrt"] {list-style-image: url(data:image/png;base64,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)} ' +
      '#menu-button[tooltiptext="Videos frei"] {list-style-image: url(data:image/png;base64,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)} ';
   var stylesheet = document.createProcessingInstruction('xml-stylesheet', 'type="text/css" href="data:text/css;utf-8,' + encodeURIComponent(css) + '"');
   document.insertBefore(stylesheet, document.documentElement);

})();