Steps to reproduce:
1) Open user attached project from the OC link
2) Open the scene Assets/Scenes/GiantsDeep.unity.
3) Press play. After several seconds you should spawn on top of one of the islands floating on the ocean surface of Giant's Deep.
4) Press '0' (zero) to teleport to the player ship.
5) Go to the pilot's seat and buckle up.
6) Lock on to the planet Giant's Deep (click the controller left stick or the left mouse button).
7) Enter the landing camera mode (press the X (Xbox) or Square (Playstation) button on the game pad or C on the keyboard).
8) Plummet towards the outer cloud layer of Giant's Deep, either by thrusting down towards (left ctrl) it or by letting gravity do its thing.
9) Upon passing into the cloud layer of Giant's Deep, note that errors are displayed in the console, and upon exiting play mode and attempting to re-enter play mode the editor crashes.

Reproduced in: 2017.4.20f2

Expected result: "Assertion failed: Called Release() on an invalid object" when cleaning command buffer following with a crash when re-entering playmode should not occur