System.NullReferenceException: Object reference not set to an instance of an object.
   at DevExpress.Xpf.Docking.Platform.TabHeaderInsertHelper.GetIntervals(ILayoutContainer container)
   at DevExpress.Xpf.Docking.Platform.TabHeaderInsertHelper..ctor(IDockLayoutContainer container, Point point, Boolean canInsertAfterAll)
   at DevExpress.Xpf.Docking.Platform.LayoutViewReorderingListener.InsertionHelper.Update(DockLayoutElementDragInfo dragInfo, Boolean isStartedAsReordering)
   at DevExpress.Xpf.Docking.Platform.LayoutViewReorderingListener.InsertTabPageCore(DockLayoutElementDragInfo dragInfo)
   at DevExpress.Xpf.Docking.Platform.LayoutViewReorderingListener.OnDragging(Point point, ILayoutElement element)
   at DevExpress.Xpf.Layout.Core.Dragging.DragServiceState.DoDragging(IView view, Point point, OperationType type)
   at DevExpress.Xpf.Layout.Core.Dragging.DragServiceState.DoDragging(IView view, Point point)
   at DevExpress.Xpf.Layout.Core.Dragging.ReorderingDragServiceState.ProcessMouseMove(IView view, Point point)
   at DevExpress.Xpf.Layout.Core.Dragging.DragService.ProcessMouseCore(IView processor, Point screenPoint, MouseEventType eventType, MouseEventArgs e)
   at DevExpress.Xpf.Layout.Core.Dragging.DragService.ProcessMouseOverride(IView view, MouseEventType eventType, MouseEventArgs ea)
   at DevExpress.Xpf.Layout.Core.UIService.ProcessMouse(IView view, MouseEventType eventType, MouseEventArgs ea)
   at DevExpress.Xpf.Layout.Core.Platform.ViewAdapter.ProcessMouseEvent(IView view, MouseEventType eventType, MouseEventArgs ea)
   at DevExpress.Xpf.Layout.Core.Platform.BaseView.OnMouseMove(MouseEventArgs ea)
   at CFETS.NTP.CLT.Infrastructure.Presentation.Workspace.Subscriber.RootUIElementMouseMove(Object sender, MouseEventArgs e)