rem: return !selectedItem || (selectedItem.disabled ? selectedItem.getAttribute("aboutURL") == "" : true); 
add: return selectedItem && (selectedItem.disabled ? selectedItem.getAttribute("aboutURL") == "" : true); 
context:   isCommandEnabled: function (aCommand)  {    var selectedItem = gExtensionsView.selected;    switch (aCommand) {    case "cmd_close":      return true;    case "cmd_useTheme":      return selectedItem && gCurrentTheme != selectedItem.getAttribute("internalName");    case "cmd_options":      return selectedItem && !selectedItem.disabled && selectedItem.getAttribute("optionsURL") != "";    case "cmd_about":      return !selectedItem || (selectedItem.disabled ? selectedItem.getAttribute("aboutURL") == "" : true);    case "cmd_homepage":      return (selectedItem && selectedItem.getAttribute("homepageURL") != "");    case "cmd_uninstall":      return selectedItem && selectedItem.getAttribute("locked") != "true";    case "cmd_update":      return true;    case "cmd_enable":      return selectedItem && selectedItem.disabled && !gExtensionManager.inSafeMode;    case "cmd_disable":      return selectedItem && selectedItem.getAttribute("locked") != "true" && !selectedItem.disabled;    case "cmd_movetop":      return (gExtensionsView.children[0] != selectedItem);    case "cmd_moveup":      return (gExtensionsView.children[0] != selectedItem);    case "cmd_movedn":      var children = gExtensionsView.children;      return (children[children.length-1] != selectedItem);#ifdef MOZ_THUNDERBIRD    case "cmd_install":      return true;   #endif    }    return false;  },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/01cfc6390b688b38ee9a497eab2f6171b135afb4/extensions.js/clean/toolkit/mozapps/extensions/content/extensions.js