title: KnockoutJS binding when source is null/undefined
body: <p>Is there a shorter/cleaner way to do the null/undefined testing?</p>
  
  <pre><code>&lt;select data-bind="options: SelectedBusinessLine() ? SelectedBusinessLine().Clusters() : [],
                                 optionsText: 'Title',
                                 value: SelectedCluster,
                                 optionsCaption: 'Select Cluster..'"&gt;
              &lt;/select&gt;
  </code></pre>
  
  <p>Instead of </p>
  
  <pre><code>data-bind="options: SelectedBusinessLine() ? SelectedBusinessLine().Clusters() : [],
  </code></pre>
  
  <p>i would like</p>
  
  <pre><code>data-bind="options: SelectedBusinessLine().Clusters(),
  </code></pre>
  
  <p>give or take the ()</p>
  
  <p>Or at least a simpler null operator check '??' SelectedBusinessLine ?? []</p>
  
  <p>Or a  binding param to auto check for null or silent fail.</p>
  
  <p>Any ideas if this is possible?</p>