add: catch(e) {} 
context: function onUnload() {  if (printProgress)  {   try    {     printProgress.unregisterListener(progressListener);     printProgress = null;   }       catch( exception ) {}  }}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/890b728028c5282cd7a90ec2638496ebac0de588/printPreviewProgress.js/clean/toolkit/components/printing/content/printPreviewProgress.js