add: return msgCompConvertible.No; 
context: function DetermineConvertibility(){    if (!msgCompose.composeHTML)        return msgCompConvertible.Plain;    try {        return msgCompose.bodyConvertible(             window.editorShell.contentWindow.document.childNodes[1]);    } catch(ex) {}}
meta: 5872	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/5872/d8d311f2e26dcdeef3c650c275a59ccc3ca4fc2f/MsgComposeCommands.js/buggy/mailnews/compose/resources/content/MsgComposeCommands.js