add: retvals.files = null; 
context: function onCancel(){  // Close the window.  retvals.buttonStatus = nsIFilePicker.returnCancel;  retvals.file = null;  return true;}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/de53ec3309b58dc4bbb49b5c278b93ecdd3ca692/filepicker.js/clean/xpfe/components/filepicker/res/content/filepicker.js