fixing context menu crash

Author: dgosbell

DaxStudio.Controls.Example/QueryPlanTreeExample.xaml

@@ -78,9 +78,6 @@
                     <Separator/>  
                     <MenuItem Header="Show Descendants with Higher Record Counts" 
                               Command="{Binding PlacementTarget.ExecuteCustomDescendantFilter, 
-                                  RelativeSource={RelativeSource FindAncestor, 
-                                  AncestorType={x:Type ContextMenu}}}"
-                              CommandParameter="{Binding PlacementTarget.SelectedItem, 
                                   RelativeSource={RelativeSource FindAncestor, 
                                   AncestorType={x:Type ContextMenu}}}"/>
                 </ContextMenu>  

DaxStudio.Controls/Controls/TreeGrid/TreeColumn.cs

@@ -260,6 +260,7 @@ private void OnExpanderPreviewMouseDownEvent(object sender, RoutedEventArgs e)
                 }
                 if (context.IsExpanded) context.IsCollapsing = true;
             }
+            e.Handled = true;
         }
 
         private void OnExpanderClick(object sender, RoutedEventArgs e)