Steps to reproduce:

1. Create new project
2. Add empty GO
3. Add Child GO to previously created GO
4. Add child to GO created in step 3 (hierarchy should be GO -> GO -> GO)
5. Drag Grandchild (GO created in step 4) to be parented by GO created in step 2 (hierarchy should be GO -> (GO; GO))
6. Drag GO which was moved in step 5 to project tab to create a prefab
7. Press ctrl+z three times
- Unity Crashes

Reproduced with: 5.3.5p5, 5.4.0b23, 5.5.0a2

5.3.5p5 has stacktrace from case 752511. 5.40b23 and 5.5.0a2 has different stactraces