Steps to reproduce:
1. Open the attached project
2. Open the MainScene scene
3. Switch platform to Windows Store
4. Play the scene
5. Verify the scene loads in the HMD/Simulator.
6. Exit the Play mode in Editor
7. Verify it stays black instead of exiting back to the cliff house

Actual results: Exiting Unity play mode leaves Windows MR in a bad state
Expected results: Windows MR should be exiting back to the cliff house

Note:
Make sure you are running Windows 10 build 16257 or higher

Reproduced with: 2017.2.0b1, 2017.2.0b8, 2017.2.0b11, 2017.3.0a7