Ruby on Rails的JQGrid错误

我在遵循这个指南, http://www.2dconcept.com/jquery-grid-rails-plugin ,以设置示例jquery数据报。

一切似乎都很好,但当我去 http://127.0.0.1:3000/users 我得到这个:

 NoMethodError in Users#index

 Showing users/index.html.erb where line #12 raised:

 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.each

 Extracted source (around line #12):

 9:     <th>Role</th>
10:   </tr>
11: 
12: <% for user in @users %>
13:   <tr>
14:     <td><%=h user.pseudo %></td>
15:     <td><%=h user.firstname %></td>

我做错了什么有什么想法吗?