title: Null-aware operator when traversing a nested map
body: <p>How do you check for nulls when accessing second level map elements?
  E.g.</p>
  
  <pre><code>var clientName = item['client']['name'];
  </code></pre>
  
  <p>will throw an exception if <code>item</code> does not contain <code>client</code>
  I'd like something like</p>
  
  <pre><code>item['client']?['name']
  </code></pre>
  
  <p>or</p>
  
  <pre><code>item['client']?.['name']
  </code></pre>
  
  <p>But that won't compile.</p>
  
  <p>Surely I can do <code>item['client']</code> twice or introduce a local var for it but that feels subpar.</p>