rem: var kids = this.mOutliner.getElementsByTagName("outlinercol"); 
add: var kids = this.mTree.getElementsByTagName("treecol"); 
context:   getColumnAt: function(aIndex)  {    var kids = this.mOutliner.getElementsByTagName("outlinercol");    return aIndex < 0 || aIndex >= kids.length ? kids[kids.length-1] : kids[aIndex];  },
meta: 5872	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/5872/d38a0937d9c93a0a9d913e2ac781e4328bb8cc73/inTreeBuilder.js/buggy/extensions/inspector/resources/content/jsutil/xul/inTreeBuilder.js