Steps to reproduce the issue:
1. Download and open attached project.
2. Open scene named "Game1".
3. Enter the play mode.
4. Notice that the Editor freezes.
5. Wait for some time until the "Fatal Error!" message appears.
6. Press "Quit" button.

Actual result:
The Editor crashes.

Expected result:
The Editor should not freeze and crash.

Reproduced with:
5.3.6p3, 5.4.0f3, 5.5.0a6, 5.5.0b1.

Cannot reproduce with:
5.1.5f1, 5.2.5f1 (because of compiler errors).

Note:
Image attached.