Firebase google auth bug？用户对象中缺少电子邮件属性

Question

var fbUsers = new Firebase('https://my-FB-subdomain.firebaseio.com/users');

var fbAuth = new FirebaseSimpleLogin(fbUsers, function(error, user) {

});
fbAuth.login('google');

文档说user object should have an email property，但传递给该回调的用户对象具有这些属性（根级别没有email属性）：

id
uid
displayName
provider
thirdPartyUserData
 - id
 - email
 - verified_email
 - name
 - given_name
 - family_name
 - link
 - picture
 - gender
 - locale
verified_email
name
given_name
family_name
link
picture
gender
locale
accessToken
firebaseAuthToken