add:  if (blankTabToRemove) tabbrowser.removeTab(blankTabToRemove); 
context: function undoCloseTab(aIndex) {  var ss = Cc["@mozilla.org/browser/sessionstore;1"].           getService(Ci.nsISessionStore);  if (ss.getClosedTabCount(window) == 0)    return;  ss.undoCloseTab(window, aIndex || 0);}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/ecd200f5945a962a77399bbc98e78fe2546e58d8/browser.js/buggy/browser/base/content/browser.js