title: doctrine findby magic null value
body: <p>I'm wondering if there is anyway to use doctrine's magic method to look for null values. For instance:</p>
  
  <pre><code>Doctrine::getTable('myClass')-&gt;findByDeletedAt(null);
  </code></pre>
  
  <p>Essentially, I want to return all records that are not deleted. I've tried the above, but it doesn't seem to work.</p>
  
  <p>Any ideas?</p>