title: Meteor/Blaze: template helper default for not found image
body: <p>I have a helper to grab an image based on a url.</p>
  
  <pre><code>Template.characterList.helpers({
    avatar_url: function(character) {
      return "http://us.battle.net/static-render/us/" + character.thumbnail;
    }
  });
  </code></pre>
  
  <p>However, sometimes, this will fail and return a 404. Ideally, what I am looking for is something similar to Flask's <code>|default</code> syntax. Eg:</p>
  
  <pre><code>&lt;img src=" {{ avatar(this) | default("http://placehold.it/300x300?text=no picture") }}" /&gt;
  </code></pre>
  
  <p>This would make an image or default to a placeholder if no picture were available.</p>
  
  <p>Is it possible to achieve this with Meteor/blaze?</p>
  
  <hr>
  
  <p>EDIT: the source of the problem comes from that the image asset on the server seems to be missing after certain amounts of character inactivity (not too surprising). so, they URL is valid, however, the GET of the image will result in a 404</p>