title: `FallbackValue` not evaluated on Binding with empty `Path` in WPF XAML?
body: <p>On a <code>Page</code> with no <code>DataContext</code> the fallback value is never evaluated, resulting in a blank <code>TextBlock</code> shown.</p>
  
  <p>For example:</p>
  
  <pre><code>&lt;TextBlock DataContext="{x:Null}" Text="{Binding  FallbackValue='HelloWorld'}"&gt;&lt;/TextBlock&gt;
  </code></pre>
  
  <p>or</p>
  
  <pre><code>&lt;TextBlock DataContext="{x:Null}" Text="{Binding Path='' FallbackValue='HelloWorld'}"&gt;&lt;/TextBlock&gt;
  </code></pre>
  
  <p>Whereas the following <code>Binding</code>, also with a null DataContext *<em>does</em>* show it's <code>FallbackValue</code>.</p>
  
  <pre><code>&lt;TextBlock DataContext="{x:Null}" Text="{Binding NonExistantProperty, FallbackValue='HelloWorld'}"&gt;&lt;/TextBlock&gt;
  </code></pre>