Merge pull request #5122 from retailcoder/GroupingGrid

Fixes all-at-once GroupingGrid collapse/expand

Author: retailcoder

Rubberduck.Core/UI/Controls/GroupingGrid.xaml

@@ -63,7 +63,7 @@
                 <Setter.Value>
                     <ControlTemplate>
                         <Expander Background="WhiteSmoke" Foreground="Black" FontWeight="SemiBold" 
-                                  IsExpanded="{Binding InitialExpandedState, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:GroupingGrid}}}">
+                                  IsExpanded="{Binding InitialExpandedState, Mode=OneWay, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:GroupingGrid}}}">
                             <Expander.Header>
                                 <StackPanel Orientation="Horizontal">
                                     <TextBlock Margin="4"