Steps to reproduce:
1. Create new Unity project
2. In Project window create Animator Controller
3. Open Animator Window
4. Right-click on “Base Layer”
5. Press “Delete” from the menu
6. Observe the Console
Actual results: “Delete” menu item is not greyed out, allowing to falsely delete the Layer for the user, throwing error in the Console
Expected results: “Delete” menu item should be greyed out, because Base Layer cannot be deleted from Layers
Reproducible with versions: 6000.0.56f1, 6000.1.16f1, 6000.2.1f1, 6000.3.0a5
Tested on (OS): Windows 11, macOS Silicon, Sequoia 15.6 (M1)