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/2007_temp/2007/9421/27ae105645a2209ebd44df3d3294111d553a8b63/bookmarks.js/buggy/suite/common/bookmarks/bookmarks.js