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: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/73f66748017128edb12ed3262b7ed2a90a325549/bookmarks.js/clean/xpfe/components/bookmarks/resources/bookmarks.js