Steps to reproduce:
1. Open the attached project
2. Open the test scene
3. Switch Platform to Windows Store
4. Make sure what a headset is unplugged and simulation mode is off in Mixed Reality Portal
5. Play the scene in Editor
6. Plug the headset or turn on simulation in Mixed Reality Portal
7. Stop the scene in Editor
8. Observe the crash

Actual results: Editor crashes when you stop playing the scene
Expected results: Editor should crash

Note:
2017.2.1p1 and 2017.3.0b11 throws the assertion but Editor does not crash:
Assertion failed: Callback unregistration failed. Callback not registered.

Reproduced with: 2017.3.0f3, 2018.1.0b1
Not reproduced with: 2017.2.1p1, 2017.3.0b11

Favro card: https://favro.com/card/c564ede4ed3337f7b17986b6/Uni-35770