title: Rails: Expected helper to define helper error?
body: <p>When accessing my Rails app locally, I get the following error when loading any page:</p>
  
  <pre><code>/!\ FAILSAFE /!\  Tue Jul 06 15:08:17 -0500 2010
  Status: 500 Internal Server Error
  Expected /my_rails_app/app/helpers/admin/article_categories_helper.rb to define Admin::ArticleCategoriesHelper
  </code></pre>
  
  <p>If I follow the <a href="https://gist.github.com/904e30559bd9c3268a07" rel="nofollow noreferrer">full trace</a>, I'm brought to this line in my application controller:</p>
  
  <pre><code>helper :all
  </code></pre>
  
  <p>If I comment out that line, everything appears to load fine.</p>
  
  <p>Also, here's the contents of my <code>/admin/article_categories_helper.rb</code> file:</p>
  
  <pre><code>module Admin::ArticleCategoriesHelper
  end
  </code></pre>
  
  <p>So, any ideas what could be causing this and how to fix it?</p>