Errors are thrown when opening a prefab while the Hierarchy window is not visible

How to reproduce:

1. Create a new project
2. Make a prefab of a Cube GameObject
3. Have the Hierarchy window next to the Scene and Game windows docked
4. Go to the Scene view so the Hierarchy window is not visible
5. Try opening the Cube prefab through the Project window
6. Observe the behavior

Actual result: Errors are thrown in the Console
Expected result: User gets redirected to the Prefab Edit mode

Reproducible with: 6000.4.0a2 (417aa67423b3), 6000.5.1f1, 6000.6.0a4 (d203f4c2ae2f)
Not reproducible with: 6000.0.78f1, 6000.3.18f1, 6000.4.0a1, 6000.6.0b1, 6000.7.0a1
Fixed in: 6000.6.0a5

Reproducible on: Windows 11
Not reproducible on: No other environments tested

Notes:

• Error message: Error while changing Stage: System.NullReferenceException: Object reference not set to an instance of an object
• Error message: Error while recovering from Stage change error: System.NullReferenceException: Object reference not set to an instance of an object
• Only reproduces with the new Hierarchy window enabled (Edit > Preferences > General > Use new Hierarchy window)