add: return null; 
context: 	QueryInterface : function(iid)	{		if(iid.equals(Components.interfaces.nsIMsgWindowCommands))			return this;		throw Components.results.NS_NOINTERFACE;	},
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/d1efe1b174955c3aea7ff9f5cc29a9bd1d79725c/mailWindow.js/clean/mailnews/base/resources/content/mailWindow.js