title: How show hide image in paperclip when no image present
body: <p>How can I prevent the image tag that calls the associated image from displaying if no image is associated with the record?</p>
  
  <pre><code>&lt;%= image_tag @agent.avatar.url %&gt;
  </code></pre>
  
  <p>...gives me the text "Missing" if there is no image associated with that agent.  I want to test to see there is an image available first, then render the above tag if the test returns true.</p>
  
  <p>Better yet, is there anyway for me to specify a default image if no image is specifically provided?</p>