Steps to reproduce:
1. Open "deletingObjectBug" project
2. Open "main" scene
3. Select one of the "PARENT(A)" children and duplicate it
4. Move duplicated child to "PARENT(B)" and attach it as "PARENT(B)" child
5. Select duplicated child and press "Revert" in the Inspector window
-Notice the duplicated child object became "PARENT(A)" with 2 children objects as "PARENT(B)" child
6. Press CTRL + Z once
-Again incorrect behaviour, one more child object gets created and 2 child objects act like one single object(attached a .mp4)
7. Press CTRL + Z couple of times again
-Unity crashes

Another way to reproduce crash is after 5 step delete newly generated "PARENT(A)" object inside "PARENT(B)"

Expected result: Unity should not crash

Reproduced on: 5.6.2f1, 2017.1.0f3, 2017.2.0b2