How to reproduce:
1. Download and open project "Crash Repro"
2. Open "das" scene
3. Enter Play Mode
4. Select enemy1 -> Enemy1 in the hierarchy (Make sure Animator window is open)

Expected result: Editor keeps working
Actual result: Editor crashes

Reproducible on: 2017.4.11f1, 2018.1.9f2, 2018.2.8f1, 2018.3.0b2
Can't test on 2017.2.3p4 because Unity crashes when importing the problem

Note: Looks like it only happens when using "enemy1" prefab
Note 2: When trying to reproduce on 2017.4.11f1, 2018.1.9f2 use the user's attached project. I tried to strip mine as much as possible, which broke it on older versions