Crash when pressing "Auto Hide" button to disable auto-hide mode

Hi, I've got an evaluation version of Docking v12 and I came into an issue writing a prototype application.

An unhandled exception is raised when I try to disable Auto Hide on a tool window using the corresponting button:

Attempt to replace within unknown parent class '<null>'.

   в ActiproSoftware.Windows.Controls.Docking.DockSite.#1t(DependencyObject #lp, DependencyObject #cm, Boolean #Ks)
   в ActiproSoftware.Windows.Controls.Docking.DockSite.#1t(DependencyObject #lp, DependencyObject #cm)
   в ActiproSoftware.Windows.Controls.Docking.DockSite.#4t(DependencyObject #lp, #ki #4j, Direction #fFf, IList`1 #JSd)
   в ActiproSoftware.Windows.Controls.Docking.DockSite.#4t(DependencyObject #lp, #ki #4j, Direction #fFf)
   в ActiproSoftware.Windows.Controls.Docking.DockSite.#en(DependencyObject #lp, Direction #fFf, Nullable`1 #eFf)
   в ActiproSoftware.Windows.Controls.Docking.ToolWindowContainer.#ZB(Object #xhb, ExecutedRoutedEventArgs #yhb)
   в System.Windows.Input.CommandBinding.OnExecuted(Object sender, ExecutedRoutedEventArgs e)
   в System.Windows.Input.CommandManager.ExecuteCommandBinding(Object sender, ExecutedRoutedEventArgs e, CommandBinding commandBinding)
   в System.Windows.Input.CommandManager.FindCommandBinding(CommandBindingCollection commandBindings, Object sender, RoutedEventArgs e, ICommand command, Boolean execute)
   в System.Windows.Input.CommandManager.FindCommandBinding(Object sender, RoutedEventArgs e, ICommand command, Boolean execute)
   в System.Windows.Input.CommandManager.OnExecuted(Object sender, ExecutedRoutedEventArgs e)
   в System.Windows.UIElement.OnExecutedThunk(Object sender, ExecutedRoutedEventArgs e)
   в System.Windows.Input.ExecutedRoutedEventArgs.InvokeEventHandler(Delegate genericHandler, Object target)
   в System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   в System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   в System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   в System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   в System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
   в System.Windows.Input.RoutedCommand.ExecuteImpl(Object parameter, IInputElement target, Boolean userInitiated)
   в System.Windows.Input.RoutedCommand.ExecuteCore(Object parameter, IInputElement target, Boolean userInitiated)
   в MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated)
   в System.Windows.Controls.Primitives.ButtonBase.OnClick()
   в System.Windows.Controls.Button.OnClick()
   в System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
   в System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
   в System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   в System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   в System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   в System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   в System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
   в System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
   в System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
   в System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   в System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
   в System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   в System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   в System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   в System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
   в System.Windows.Input.InputManager.ProcessStagingArea()
   в System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
   в System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
   в System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
   в System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   в System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   в MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   в MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
   в System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   в MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
   в System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
   в MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   в MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
   в System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
   в System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
   в System.Windows.Application.RunDispatcher(Object ignore)
   в System.Windows.Application.RunInternal(Window window)
   в System.Windows.Application.Run(Window window)
   в System.Windows.Application.Run()
   в DockTest2.App.Main() в C:\Work\DockTest2\obj\x86\Debug\App.g.cs:строка 0
   в System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   в System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   в Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   в System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   в System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
   в System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   в System.Threading.ThreadHelper.ThreadStart()

Solution source: https://dl.dropbox.com/u/17443884/DockTest3.zip

WTR video: https://dl.dropbox.com/u/17443884/DockingTest3.avi