add: document.getElementById("editFeed").disabled = !item || item.container; 
context:   onSelect: function ()   {    var properties, item;    var seln = this.mTree.view.selection;    item = this.mView.getItemAtIndex(seln.currentIndex);          this.updateFeedData(item);            document.getElementById("removeFeed").disabled = !item || item.container;  },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/09674c25572db974a74c139877a1448a01cb8a14/feed-subscriptions.js/clean/mail/extensions/newsblog/content/feed-subscriptions.js