How to reproduce:
1. Open user-submitted project (Zombie.zip)
2. Open the lab Scene
3. Make sure Editor scripts are set to 'Recompile and Continue Playing' in Preferences and Enter Play Mode
4. Open UIManager.cs script
5. Edit the script and save it
6. Go back to the Editor(it should recompile the scripts)
7. Exit Play Mode

Expected result: the Editor does not crash
Actual result: the Editor crashes

Reproducible with: 2019.3.0a3, 2019.3.13f1, 2020.1.0b9, 2020.2.0a11
Not reproducible with: 2018.4.23f1, 2019.3.0a2
Could not test with: 2017.4.40f1(project packages incompatible)

Notes:
May crash immediately upon recompiling
May take multiple tries to reproduce