Javascript AMP-转发页

我有一个AMP网站，那里有一个注册表格。 在后端有验证，如果验证失败，浏览器应该转发到新的url

    xhr.onreadystatechange = function () {
        if (xhr.readyState === 4 && xhr.status === 200) {
            quoteSent();
        }else if (xhr.readyState === 4 && xhr.status === 307){
            let url = xhr.responseText;
            console.log("url: " + url); //<-- prints properly to log
            setTimeout(function(){document.location.href = url;},1); //<-- Uncaught TypeError:
        }else{
            quoteNotSent();
        }
    };

url: https://example.com/quote/c1
log.js:264 [amp-script] Uncaught TypeError: Cannot set property 'href' of undefined
    at (amp-script%5Bscript=%22quoteFormScript%22%5D.js:64)