title: Angular2 how to handle value of date pipe is null
body: <p>I have template using date pipe like this</p>
  
  <pre><code>{{value | date: 'dd/MM/yyyy'}}
  </code></pre>
  
  <p>this <code>value</code> is <code>null</code></p>
  
  <p>How to handle this if my value null i got string <code>'object not match'</code>?</p>