Objects created from xref-scene show up in layer and material mode

[Pjanssen]

What steps will reproduce the problem?

1. Create a scene with a single object.
2. Save the scene.
3. Create a new scene.
4. Use xref-scene to xref the scene created at step 1.
5. Open the Outliner and switch to layer and material mode.

What is the expected output? What do you see instead?
The objects from the xref-ed scene should not be visible in the Outliner.