title: Making variable optional in underscore.js template
body: <p>I have this code:</p>
  
  <pre><code>_.templateSettings = {interpolate : /\{\{(.+?)\}\}/g};
  
  var _d = _.template($('#_d').html());
  
  $.get('/foo', function(data) {
      $('#output').html(_d(data));
  });
  </code></pre>
  
  <p>and in HTML:</p>
  
  <pre><code>&lt;div id="_d"&gt;
      {{name}} {{phone}}
  &lt;/div&gt;
  &lt;div id="output"&gt;&lt;/div&gt;
  </code></pre>
  
  <p><code>/foo</code> returns something like <code>{"name":"joe","phone":"12345"}</code>, but sometimes it doesn't have <code>phone</code> thus simply returns <code>{"name":"joe"}</code>, which will choke template evaluation thus nothing gets printed in <code>output</code>. How do I make a variable optional?</p>
  
  <p><strong>EDIT:</strong> <code>/foo</code> is beyond my control</p>