add:  if  (browser.popupUrls.length == 0) return false; 
context: function createShowPopupsMenu(parent) {  while (parent.lastChild && parent.lastChild.hasAttribute("uri"))    parent.removeChild(parent.lastChild);  var browser = getBrowser().selectedBrowser;        for (var i = 0; i < browser.popupUrls.length; i++) {    var menuitem = document.createElement("menuitem");    menuitem.setAttribute("label", gNavigatorBundle.getFormattedString('popupMenuShow', [browser.popupUrls[i].spec]));    menuitem.setAttribute("uri", browser.popupUrls[i].spec);    menuitem.setAttribute("features", browser.popupFeatures[i]);    parent.appendChild(menuitem);  }  return true;}
meta: 5872	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/5872/0521424a3f947d1aacfc4cd877c74c4e65a786de/navigator.js/clean/suite/browser/navigator.js