devise + omniauth undefined方法`find'for Symbol：Class error

Question

 NoMethodError in Projects#index

Showing /home/dave/Documents/exercises/todo/app/views/layouts/application.html.erb where line #18 raised:

undefined method `find' for Symbol:Class

Extracted source (around line #18):

15: 
16:   <div id="container">
17:     <div id="user_nav">
18:       <% if user_signed_in? %>
19:         Sign in as <%= current_user.email %>. Not you?
20:         <%= link_to "Sign out", destroy_user_session_path %>
21:       <%else %>

为什么我收到此错误消息？

符号的未定义方法`find'：Class

即时使用rails 3.0.7并设计1.1.rc0

基于本教程http://media.railscasts.com/videos/236_omniauth_part_2.mov

我只是捆绑安装设备1.3.4并更改了secret_token或清除会话db和* 然后启动并运行 *

只是为了让你知道，有些人可能会调查一些导致这个问题的原因。