Merge pull request #780 from Alliance-Network/GridViewColumnHeader_Thumb

Fix Thumb of GridViewColumnHeader.

Author: Keboo

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.ListView.xaml

@@ -90,6 +90,7 @@
                     <DockPanel>
                         <Thumb x:Name="PART_HeaderGripper"
                                DockPanel.Dock="Right"
+                               Margin="0,0,-8,0"
                                Style="{StaticResource MaterialDesignGridColumnHeaderGripper}" />
                         <Border x:Name="HeaderBorder"
                                 Padding="{TemplateBinding Padding}"