Floating window without a content is shown as black rectangle and stays till the main window is loaded.

Steps to reproduce:

1. Go to project MLibTest.
2. Replace MainWindow.xaml.cs with the file attached. [The only difference with the current version is call to the Thread.Sleep() in OnLayoutLoaded_Event to imitate some activity.]
3. Compile the project.
4. Go to application folder and replace AvalonDock.Layout.config with the file attached.
5. Run the application. Black rectangle of the floating window stays at the screen till main window is shown.

Steps co create AvalonDock.Layout.config with test content:

1. Go to the application folder.
2. Delete AvalonDock.Layout.config.
3. Run the application.
4. Undock FileStatsTool.
5. Switch it off from main menu (Tools -> File stats).
6. Save layout.

AvalonDock.Layout.config.txt
MainWindow.xaml.cs.txt