rem: outlinerSelection.clearSelection(); 
add: if (outlinerSelection) outlinerSelection.clearSelection(); 
context: function ClearThreadPaneSelection(){  try {    if (gDBView) {      var outlinerView = gDBView.QueryInterface(Components.interfaces.nsIOutlinerView);      var outlinerSelection = outlinerView.selection;      outlinerSelection.clearSelection();     }  }  catch (ex) {    dump("ClearThreadPaneSelection: ex = " + ex + "\n");  }}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/938770831965cde1ef5c4ce945b768186518efae/msgMail3PaneWindow.js/clean/mailnews/base/resources/content/msgMail3PaneWindow.js