title: Rails partial with optional variable not working
body: <p>I'm not sure what's going on here but the following throws an error on render:</p>
  
  <pre><code>&lt;%= render 'clients/clients_table', special: true %&gt; 
  </code></pre>
  
  <p>and in my partial I have:</p>
  
  <pre><code>&lt;% if defined?(:special) %&gt;
      &lt;p&gt;&lt;%= special %&gt;&lt;/p&gt; &lt;!-- line with error --&gt;
  &lt;% else %&gt;
      &lt;p&gt;No&lt;/p&gt;
  &lt;% end -%&gt;
  </code></pre>
  
  <p>This throw the error:</p>
  
  <pre><code>undefined local variable or method `special' for #&lt;#&lt;Class:0x007fa20fbb0310&gt;:0x007fa20cb986a0&gt;
  </code></pre>
  
  <p>When I try to display <code>local_assigns.has_key?(:special)</code> it also shows <code>false</code>.  Any idea what's going on?</p>