Method insertElement causes error in IE if editable hasn't been yet focused

[Jakub Ś]

Insert below code into replacebycode sapmle:

editor.on('instanceReady', function(){
	var elem = new CKEDITOR.dom.element( 'pre' );
	editor.insertElement(elem); //error in IE
	//editor.editable().append(elem); //works
});

When you load the page you will get:
Message: 'undefined' is empty or not an object
Line: 299
URI: /ckeditor4_git/core/editable.js

Problem can be reproduced from CKEditor 4.3 in all versions of IE.