Steps to reproduce:

1. Open the attached project
2. Open TestAnim Animation Controller
3. Create a new Layer
4. Switch to the Parameters tab
5. Perform the Undo action

Actual results: "MissingReferenceException: The object of type 'UnityEditor.Animations.AnimatorStateMachine' has been destroyed but you are still trying to access it." error is spammed in the console after performing the Undo action

Expected results: No warnings or errors are thrown after performing an Undo action

Reproducible with versions: 2022.3.61f1, 6000.0.48f1, 6000.1.1f1, 6000.2.0a10

Tested on (OS): macOS 15.4.1

Notes:

• If Undo is performed while in the Layers tab, the issue does not occur