title: How to check if dictionary key is null
body: <p>I have json variable:</p>
  
  <pre><code>"variable": {
      "changed": false,
      "data": null,
      "failed": false,
      "index": "135"
  }
  </code></pre>
  
  <p>How to test if <code>variable.data</code> is null? I tried these, none works:</p>
  
  <pre><code>when: variable.data is null
  when: variable.data is None
  when: variable.data is NoneType
  when: variable.data == 'None'
  when: variable.data == 'null'
  when: variable.data == ''
  </code></pre>
  
  <p>getting either error</p>
  
  <blockquote>
    <p>The error was: template error while templating string: no test named xxx</p>
  </blockquote>
  
  <p>or "when" conditional failing.</p>