rem: if (aEvent.shiftKey) 
add: if (aEvent && aEvent.shiftKey) 
context:   shouldLoadTabInBackground: function(aEvent)  {    var loadInBackground = PREF.getBoolPref("browser.tabs.loadInBackground");    if (aEvent.shiftKey)      loadInBackground = !loadInBackground;    return loadInBackground;  },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/4f35327af22fb2f55d166ef742116d9b55e9f1bc/bookmarks.js/buggy/xpfe/components/bookmarks/resources/bookmarks.js