ruby-on-rails - 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:in apply_omniauth' app/controllers/authentications_controller.rb:18:increate'

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

我应该怎么办？

更新：

我发现了错误，但在登录后，回调还是来到了注册页面。我也发现模型中没有保存任何内容。