When sorting a table I get the following stacktrace. 06.12.2016 15:39:34 Error General Object reference not set to an instance of an object. System.NullReferenceException: Object reference not set to an instance of an object. at System.Windows.Controls.ItemContainerGenerator.Remove(GeneratorPosition position, Int32 count, Boolean isRecycling) at Telerik.Windows.Controls.TreeView.TreeViewPanel.CleanupRange(IList children, IItemContainerGenerator generator, Int32 startIndex, Int32 count) at Telerik.Windows.Controls.TreeView.TreeViewPanel.CleanupContainers(Int32 firstViewport, ItemsControl itemsControl) at Telerik.Windows.Controls.TreeView.TreeViewPanel.MeasureOverride(Size constraint) at System.Windows.FrameworkElement.MeasureCore(Size availableSize) at System.Windows.UIElement.Measure(Size availableSize) at MS.Internal.Helper.MeasureElementWithSingleChild(UIElement element, Size constraint) at System.Windows.Controls.ItemsPresenter.MeasureOverride(Size constraint) at System.Windows.FrameworkElement.MeasureCore(Size availableSize) at System.Windows.UIElement.Measure(Size availableSize) at System.Windows.Controls.Grid.MeasureCell(Int32 cell, Boolean forceInfinityV) at System.Windows.Controls.Grid.MeasureCellsGroup(Int32 cellsHead, Size referenceSize, Boolean ignoreDesiredSizeU, Boolean forceInfinityV, Boolean& hasDesiredSizeUChanged) at System.Windows.Controls.Grid.MeasureOverride(Size constraint) at System.Windows.FrameworkElement.MeasureCore(Size availableSize) at System.Windows.UIElement.Measure(Size availableSize) at System.Windows.Controls.Control.MeasureOverride(Size constraint) at Telerik.Windows.Controls.RadTreeViewItem.MeasureOverride(Size availableSize) at System.Windows.FrameworkElement.MeasureCore(Size availableSize) at System.Windows.UIElement.Measure(Size availableSize) at Telerik.Windows.Controls.TreeView.TreeViewPanel.MeasureOverride(Size constraint) at System.Windows.FrameworkElement.MeasureCore(Size availableSize) at System.Windows.UIElement.Measure(Size availableSize) at MS.Internal.Helper.MeasureElementWithSingleChild(UIElement element, Size constraint) at System.Windows.Controls.ItemsPresenter.MeasureOverride(Size constraint) at System.Windows.FrameworkElement.MeasureCore(Size availableSize) at System.Windows.UIElement.Measure(Size availableSize) at System.Windows.Controls.Grid.MeasureCell(Int32 cell, Boolean forceInfinityV) at System.Windows.Controls.Grid.MeasureCellsGroup(Int32 cellsHead, Size referenceSize, Boolean ignoreDesiredSizeU, Boolean forceInfinityV, Boolean& hasDesiredSizeUChanged) ...