How to reproduce:
1. Clone or download "EntityComponentSystemSamples" project from Unity Technologies GitHub page: https://github.com/Unity-Technologies/EntityComponentSystemSamples
2. Open "Sample" project
3. Open "DungeonFirstExample" scene
4. Exit Unity

Expected result: Unity closes.
Actual result: Unity crashes.

Regression first introduced in - 2018.2.0a9
Reproducible with - 2018.2.0a9, 2018.2.0b8
Not reproducible with - 2018.1.0f1, 2018.1.5f1, 2018.3.0a1
Could not test with - 2017.1.4p1, 2017.2.3p1, 2017.4.5f1, 2018.1.0a1, 2018.1.0b13 (does not have all the required packages to compile the project)

Notes:
- Happens when "DungeonFirstExample" or "RotationExample" scenes were opened.
- 2018.3.0a1 had compiler errors which may have prevented the crash from happening.