Errors displayed when undoing/redoing after creating a prefab of child object and then saving the scene and deleting the child object.
Refer to the attached Video.

Steps to Reproduce:
1. Create a New Project
2. Hierarchy > Create Cube > Create Child
3. Create a Prefab of Child Object
4. Undo > Redo
5. Save Scene
6. Delete Child Object > Undo

Actual Result:
Errors in Console after each of the steps 4 5 & 6

Expected Result:
No errors while performing undo-redo actions

Reproducible with:
2021.1.0a10, 2021.1.0a2

Working fine in:
2021.1.0a1

Environment:
Windows 10 and macOS 10.15

License type: Pro