How to reproduce:
1. Create a new project
2. Open Console Window and Animator Window with Layers view active
3. Create a new Animation Controller and select it
4. In Animator window create a new empty State and select it
5. Create a new layer and keep it selected
6. Do Undo operation twice and observe Console Window

Expected result: no new errors appear in Console Window
Actual result: one or multiple IndexOutOfRangeException errors appear in Console Window

Reproducible with: 2017.4.35f1, 2018.4.13f1, 2019.2.14f1, 2019.3.0f1, 2020.1.0a15