Fix NonClientAreaContent.

src/Shared/HandyControl_Shared/Themes/Styles/Window.xaml

@@ -189,6 +189,7 @@
                                         </MultiBinding>
                                     </TextBlock.Visibility>
                                 </TextBlock>
+                                <ContentPresenter WindowChrome.IsHitTestVisibleInChrome="True" Grid.Column="2" x:Name="ContentPresenterMain" Content="{TemplateBinding NonClientAreaContent}"/>
                             </Grid>
                         </Grid>
                     </hc:SimplePanel>