How to reproduce:
1. Open the user's attached project
2. Open scene Scenes/MovementPrototype
3. In the Hierarchy window, select the GameObject "Player-Cat"
4. At the top of the Inspector view, select "Open" next to "Prefab"
5. Go to Animation Rigging at the top of the Editor window and select Rig Setup
6. Go to Edit -> Undo Rig 1 or press Ctrl+Z to undo the Rig Setup

Expected result: no crash occurs
Actual result: crash occurs

Reproducible with: 1.1.1 (2021.2.0a9, 2021.2.3f1)
Not reproducible with: 1.1.1 (2020.3.23f1, 2021.1.28f1, 2021.2.0a8)
Could not test with: 0.2.7-preview (2019.4.32f1) (cannot resolve errors after downgrading), 1.1.1 (2022.1.0a15) (crash on launching the user's project)

Notes: sometimes the crash occurs after a slight delay