title: Rails - validates all blank false but still can't be blank?
body: <p>In my model for a Product, I have:</p>
  
  <pre><code> validates :description,        allow_blank: true, presence: false
  </code></pre>
  
  <p>And when I try to seed some Products with the description left blank, I get the following error in my Terminal:</p>
  
  <pre><code>rake aborted!
  Validation failed: Description can't be blank
  </code></pre>
  
  <p>Can anyone tell me why this is happening? Driving me crazy.</p>