omn​​iauth facebook的回调显示错误

Question

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.[]

app / models / user.rb：9：apply_omniauth' app/controllers/authentications_controller.rb:18:in创建'

我一直在从教程http://railscasts.com/episodes/235-omniauth-part-1和http://railscasts.com/episodes/236-omniauth-part-2中尝试这一点。

我该怎么办？

更新

我发现了这个错误但仍然在登录后，回调进入了注册页面。我也发现模特没有保存。