add: return null; 
context: 	QueryInterface : function(iid)	{		if(iid.equals(Components.interfaces.nsIMsgWindowCommands))			return this;		throw Components.results.NS_NOINTERFACE;	},
meta: 5459	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/5459/977a2827a9ed2a56efc59e7e9a423e0c4e06bdf6/mailWindow.js/buggy/mailnews/base/resources/content/mailWindow.js