unable to save floating documents or documents in new tab group

[arnovb-github]

I discovered an issue likely pertaining to the docking manager. When you drag a window outside the container (i.e., make it a floating window), it cannot be saved. At this point, the ActiveDocument property in MainWindow.xaml.cs returns null.

Also, when you create a new tab group, you also cannot save documents from there.

I wonder if this is by design?