rem: if (dirTree.currentIndex < 0) return null; 
add:   try { if (dirTree.currentIndex < 0) return null; 
context: function GetSelectedDirectory(){  if (dirTree.currentIndex < 0)    return null;  var selected = dirTree.contentView.getItemAtIndex(dirTree.currentIndex);  return selected.id;}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/fd26233979f82786ad999cbf7f9f49086268b9e7/abCommon.js/clean/mailnews/addrbook/resources/content/abCommon.js