CRM 2015 Microsoft app xpathevaluator' is undefined

Question

We are using crm 2015 and it is working without a problem. All code is executed correctly in IE and in Chrome. But when we try to use the crm app from Microsoft we get the error: 'xpathevaluator' is undefined.

I think it is the xrmservicetoolkit that is throwing the error.

    if (typeof (node.selectSingleNode) != "undefined") {
        return node.selectSingleNode(xpathExpr);
    } else {
        var xpe = new XPathEvaluator();
        var xPathNode = xpe.evaluate(xpathExpr, node, _NSResolver, XPathResult.FIRST_ORDERED_NODE_TYPE, null);
        return (xPathNode != null) ? xPathNode.singleNodeValue : null;
    }