Commented Unassigned: avalondock invalid window handle [22233]

Hi, my tester is getting such an exception after having the app longer time in background:

System.ComponentModel.Win32Exception

Message:
Neplatný popisovač okna ------> it means "invalid window handle"

Stack Trace:
at MS.Win32.UnsafeNativeMethods.GetParent(HandleRef hWnd)
at System.Windows.Interop.HwndHost.CalculateAssignedRC(PresentationSource source)
at System.Windows.Interop.HwndHost.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at Xceed.Wpf.AvalonDock.Controls.LayoutAutoHideWindowControl.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at System.Windows.Interop.HwndHost.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

NativeErrorCode:
1400

ErrorCode:
-2147467259

TargetSite:
IntPtr GetParent(System.Runtime.InteropServices.HandleRef)

Source:
WindowsBase

HResult:
-2147467259

it is perhaps corrected in the 2.9.0 plus edition. is there some solution for the community edition?

Thanks, Ludek.
Comments: ** Comment from web user: lalle1 **

We get the same problem with version 2.8 on windows 2012