Little hack to prevent an exception

inabox.wpf/DynamicGrid/UIComponent/DynamicGridTreeUIComponent.cs

@@ -719,6 +719,8 @@ public class DynamicGridTreeUIComponent<T> : IDynamicGridUIComponent<T>, IDynami
                         var border = new FrameworkElementFactory(typeof(Border));
                         border.SetValue(Border.BackgroundProperty, new SolidColorBrush(Colors.Gainsboro));
                         border.SetValue(Border.PaddingProperty, new Thickness(4));
+                        border.Name = "PART_HeaderCellBorder";
+
                         var img = new FrameworkElementFactory(typeof(Image));
                         img.SetValue(Image.SourceProperty, image);
                         border.AppendChild(img);