NullReferenceException in LayoutDocumentControl.OnModelChanged

[Khaos66]

Hi, when I use Drag&Drop to move a document and dock it in a new panel a NullReferenceException is thrown in OnModelChanged.

It seems that the line SetLayoutItem(Model.Root.Manager.GetLayoutItemFromModel(Model)); is the problem. The debugger shows that Model.Root is null. The CallStack is quite long:

AvalonDock.dll!AvalonDock.Controls.LayoutDocumentControl.OnModelChanged(System.Windows.DependencyPropertyChangedEventArgs e) Line 52	C#
AvalonDock.dll!AvalonDock.Controls.LayoutDocumentControl.OnModelChanged(System.Windows.DependencyObject d, System.Windows.DependencyPropertyChangedEventArgs e) Line 43	C#
[...]
AvalonDock.dll!AvalonDock.DockingManager.InternalRemoveLogicalChild(object element) Line 1441	C#
AvalonDock.dll!AvalonDock.Controls.LayoutFloatingWindowControl.FloatingWindowContentHost.DestroyWindowCore(System.Runtime.InteropServices.HandleRef hwnd) Line 137	C#
[...]
AvalonDock.dll!AvalonDock.Controls.LayoutFloatingWindowControl.OnClosed(System.EventArgs e) Line 536	C#
AvalonDock.dll!AvalonDock.Controls.LayoutDocumentFloatingWindowControl.OnClosed(System.EventArgs e) Line 150	C#
[...]

As you can see the method LayoutDocumentFloatingWindowControl.OnClosed is called before the OnModelChanged.
There the Root is disposed before the window is closed:

ILayoutRoot root = Model.Root;
if (root != null)
{
	root.Manager.RemoveFloatingWindow(this);
	root.CollectGarbage();
}
if (_overlayWindow != null)
{
	_overlayWindow.Close();
	_overlayWindow = null;
}
base.OnClosed(e);
[...]

Not sure why this is only a problem in my project. But looks logical to me, that a NullReferenceException is thrown.

[Khaos66]

@Dirkster99 I created a PR #241 for this issue. Please accept it and release a new version via Nuget. I'm stuck on this...

[Khaos66]

Thank you for releasing a new Nuget <3