title: Undefined method `model_name' in Simple_form
body: <p>So i have this 2-step Twitter Sign in and at the page where the user must enter his Email i get an undefined method error.</p>
  
  <p><strong>My Form</strong> :</p>
  
  <pre><code>&lt;%= simple_form_for(@user, :as =&gt; "user", :url =&gt; account_create_path, :html =&gt; {:class =&gt; "form-inline"}) do |f| %&gt;
    &lt;%= f.input :email, :placeholder =&gt; User.human_attribute_name(:email), :class =&gt; "input-medium" %&gt;
    &lt;%= f.submit "Finish registration", :class =&gt; "btn btn-small" %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>I think that it's a Syntax problem, but as i am fairly new to Rails i cant figure out what is wrong. Google wont tell me either :)</p>
  
  <p>my <strong>Accounts_controller.rb</strong>:</p>
  
  <pre><code>def create
          data = session["devise.omniauth_data"]
          data[:email] = params[:user][:email]
          user = User.find_for_twitter_oauth(data)
          user.email = data[:email]
  
          if user.save
              flash[:notice] = I18n.t "devise.registrations.signed_up_but_unconfirmed"
              redirect_to root_path
          else
              flash[:error] = I18n.t "devise.omniauth_callbacks.failure",
                                                           :kind =&gt; data[:provider].titleize,
                                                           :reason =&gt; user.errors.full_messages.first
              render "users/omniauth_callbacks/add_email"
          end
      end
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/68Wv0.png" alt="enter image description here"></p>