To reproduce:

1. Download attached project from the link and open in Unity
2. Open "UFPS_CleanScene" scene
3. Enter Play mode
4. Wait till player drops on the ground and observe that Unity does not crash
5. Exit Play mode
6. Build and Run project
7. Wait till player drops on the ground

Expected result: After the player drops on the ground, Unity standalone does not crash
Actual result: After the player drops on the ground, Unity standalone crashes

Notes:
- This issue reproduces on both Windows and OSX standalone
- A stack trace is shared in Comments section
- Could not check on Unity 2018.3 because project becomes corrupted

Reproduced on Unity 2018.2.0b8 and 2018.2.0f1
Not reproduced on Unity 2018.1.7f1 and 2018.2.0b7
Regression on Unity 2018.2.0b8