How to reproduce:
1. Open the attached "ProtoJump.zip" project
2. Double click on "Speedy" prefab in the Prefab folder to enter Prefab Mode
3. Note that this prefab has a script with (removed) in the title
4. Open the "AutoMovement2D" script in Visual Studio and edit anything
5. Return to the Unity and make sure the Prefab is selected
6. Observe the Inspector

Expected Behavior: The Inspector refreshes and everything is as it was before Script editing
Actual Behavior: The Inspector is broken, fake window section appears next to the inspector, the script is gone from the inspector, editor throws NullReferenceExceptions

Reproducible with: 2018.3.0b8, 2018.3.3f1
Not Reproducible with: 2018.3.0b7 and 2019.1, 2019.2 streams, as the inspector is reworked there, also 2017.4 as it does not have Prefab Mode

Note: The bug does not seem to reproduce if the prefab is not selected.