Created Unassigned: System.NullReferenceException in DataGrid wtih Groups [22365]

Hi!

When the application is running for a long time, throw unhadled exceptions:

System.NullReferenceException System.String GetItemStatusCore()
in Xceed.Wpf.DataGrid.Automation.DataGridGroupAutomationPeer.GetItemStatusCore()
in System.Windows.Automation.Peers.AutomationPeer.UpdateSubtree()
in System.Windows.Automation.Peers.AutomationPeer.UpdateSubtree()
in System.Windows.Automation.Peers.AutomationPeer.UpdatePeer(Object arg)
in System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
in MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)