title: Instance variable nil in one view, not in another
body: <p>I'm working on a project in Ruby on Rails (Ruby v.2.2.8, Rails 5.1.4) and have encountered a very strange issue.</p>
  
  <p>For my show method in the controller, I have:</p>
  
  <pre><code>def show
      @county = County.find(params[:id])
  end
  </code></pre>
  
  <p>And it works. For update, I have.</p>
  
  <pre><code>def update
      @county = County.find(params[:id])
  
      if @county.update(county_params)
          redirect_to @county
      else
          render 'edit'
      end
  end
  </code></pre>
  
  <p>In my 'edit', I consistently get an error that @county is nil. The error page indicates that the parameters are being passed as:</p>
  
  <pre><code>{'id'=&gt;4}
  </code></pre>
  
  <p>as an example. When I use find_by from the rails console, the item is found.</p>
  
  <p>Is there something here I'm missing?</p>
  
  <p>ETA: View Code</p>
  
  <pre><code>&lt;%= form_with model: @county, local: true do |form| %&gt;
  
      &lt;% if @county.errors.any? %&gt;
           &lt;div id="error_explanation"&gt;
                &lt;h2&gt;
                    &lt;%= pluralize(@county.errors.count, "error") %&gt; prohibited
      this county from being saved:
                &lt;/h2&gt;
                &lt;ul&gt;
                  &lt;% @county.errors.full_messages.each do |msg| %&gt;
                    &lt;li&gt;&lt;%= msg %&gt;&lt;/li&gt;
                  &lt;% end %&gt;
                &lt;/ul&gt;
          &lt;/div&gt;
     &lt;% end %&gt;
     &lt;p&gt;
      &lt;%= form.label :name %&gt;&lt;br&gt;
      &lt;%= form.text_field :name %&gt;
    &lt;/p&gt;
  
    &lt;p&gt;
      &lt;%= form.label :shortname %&gt;&lt;br&gt;
      &lt;%= form.text_field :shortname %&gt;
    &lt;/p&gt;
  
    &lt;p&gt;
      &lt;%= form.submit %&gt;
    &lt;/p&gt;
  
  &lt;% end %&gt;
  </code></pre>
  
  <p>ETA Routes for Counties:</p>
  
  <pre><code>counties GET /counties(.:format) counties#index
           POST /counties(.:format) counties#create
  new_county GET /counties/new(.:format) counties#new
  edit_county GET /counties/:id/edit(.:format) counties#edit
  county GET /counties/:id(.:format) counties#show
         PATCH /counties/:id(.:format) counties#update
         PUT /counties/:id(.:format) counties#update
         DELETE /counties/:id(.:format) counties#destroy
  </code></pre>
  
  <p>The error occurs at /counties/:id/edit</p>