add: if (!command) {   return; } 
context: function ltnInitializeMode(){  gCurrentMode = 'mail';  // per default we check the mail command.  // we don't need to do anything else since the  // mail view is also shown by default.  var command = document.getElementById("switch2mail");  command.setAttribute("checked", "true");    var printbutton = document.getElementById("button-print");  printbutton.setAttribute("mode", "calendar");  var deletebutton = document.getElementById("button-delete");  deletebutton.setAttribute("mode", "calendar");}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/9421/49d99658257e01d5bb14d94382a0b2604eb4fa45/messenger-overlay-toolbar.js/buggy/calendar/lightning/content/messenger-overlay-toolbar.js