title: E_UNEXPECTED UWP Catastrophic Failure
body: <p>I am getting the following:</p>
  
  <blockquote>
    <p>Catastrophic failure (Exception from HRESULT: 0x8000FFFF
    (E_UNEXPECTED))</p>
  </blockquote>
  
  <p>when the ListView attribute is set to Null in the Visual State. It makes no sense, why does VS and Blend complain? </p>
  
  <pre><code>&lt;VisualState.Setters&gt;
       &lt;Setter Target="listView.(Selector.IsSynchronizedWithCurrentItem)" Value="{x:Null}"/&gt;
  &lt;/VisualState.Setters&gt;
  </code></pre>
  
  <p><strong>EDIT</strong><br>
  A similar issue:</p>
  
  <pre><code> &lt;VisualState.Setters&gt;
     &lt;Setter Target="NumberButtonBox.(RelativePanel.RightOf)" Value="{x:Null}" /&gt;
     &lt;Setter Target="NumberButtonBox.(RelativePanel.Below)" Value="GridPlaceholder" /&gt;
  &lt;/VisualState.Setters&gt;
  </code></pre>
  
  <p>where NumberButtonBox is defined as</p>
  
  <pre><code>&lt;Viewbox x:Name="NumberButtonBox" RelativePanel.RightOf="GridPlaceholder" MaxWidth="250" MaxHeight="450" MinWidth="200"&gt;
  </code></pre>
  
  <p>The error shows <em>only</em> on the setter using a value of <code>{x:Null}</code>, not on the other line. Changing the order of the Setter lines has no effect.</p>
  
  <p>Is setting the property to Null in this way the correct way to clear this value? At runtime it does work, just the editor has issues with this.</p>