How to reproduce:
1. Open the user's attached "Probuilder Bug.zip" project
2. Open the "SampleScene" Scene
3. Create a new Probuilder Cube in the Hierarchy window (Right-click -> 3D Object -> Probuilder Cube)
4. Drag the "Cube" GameObject into the Project window to make a Prefab Asset
5. Open the "Cube" Prefab in the Prefab Mode
6. Unselect the "Cube" GameObject in the Hierarchy window
7. Create a child Probuilder Cube in the Hierarchy window (Right-click -> 3D Object -> Probuilder Cube)
8. Duplicate the created child by pressing CTRL + D on the keyboard
9. Select the parent GameObject
10. Press "Center Pivot" in the Probuilder window
11. Observe the Console log

Expected result: No errors are thrown in the Console log
Actual result: "NullReferenceException: Object reference not set to an instance of an object" error message is thrown in the Console log

Reproducible with: 4.1.0, 4.2.1, 4.3.0-preview.1 (2020.1.6f1, 2020.2.0b3)
Not reproducible with: 4.3.0-preview.2, 4.4.0 (2020.1.6f1, 2020.2.0b3)
Could not test with: 2018.4.27f1, 2019.4.10f1 (Cannot make a Probuilder cube child in the Prefab Mode)