Original Issue: #1481

I have an application using the AvalonDock library, and to fix an issue with new documents not showing content correctly (#1480), we have to set the IsActive property on the LayoutDocument to true in the BeforeInsertDocument method of the ILayoutUpdateStrategy implementation.

With this setup, the library throws a Null Reference Exception under these circumstances:

1. Open enough new documents such that the tab headers fill the available width of the screen.
2. The next document you open will be added at the start of the list instead of the end
3. Click inside the document to give it focus
4. Open another new document
5. AvalonDock throws a Null Reference Exception

I have been able to produce a sample application that produces the same error; which is simply the DocumentOpenSample modified to set the IsActive property as described.

DocumentOpenSample.zip