title: Rails - Paperclip validating attachment size when it shouldn't be?
body: <p>I've got a rails model using Paperclip that looks like this:</p>
  
  <pre><code>  has_attached_file :image, :styles =&gt; { :normal =&gt; ['857x392#', :png] },
                      :url =&gt; '/assets/pages/:id/:basename.:extension',
                      :path =&gt; ':rails_root/public/assets/pages/:id/:basename.:extension'
  
    validates_attachment_size :image, :less_than =&gt; 2.megabytes
  </code></pre>
  
  <p>When attempting to create a record of this model without an attachment to upload, the validation error is returned:</p>
  
  <blockquote>
    <p>There were problems with the following
    fields:</p>
  
  <pre><code>* Image file size file size must be between 0 and 2097152 bytes.
  </code></pre>
  </blockquote>
  
  <p>I've tried passing both :allow_blank => true and :allow_nil => true after the validation statement in the model, but neither have worked. </p>
  
  <p>How can I allow the :image parameter to be blank?</p>