How to reproduce:
1. Open the attached "Test.zip" project or create a new one
2. In the Menu bar, select "Edit/ Project Settings..."
3. In the Project Settings window, make sure that the "Script Execution Order" tab is selected
4. Enter the Play mode
5. Exit the Play mode
6. Observe the Console window

Expected result: The Console does not contain any errors and Project Settings window is not broken.
Actual result: There are multiple errors in the Console and GUI of the Script Execution Order tab is broken (it is empty, hovering the mouse over it produces even more errors).

Reproducible with - 2018.3.0a4, 2018.3.3f1, 2019.1.0a15, 2019.2.0a2
Not reproducible with - 2017.4.19f1, 2018.3.0a3

Note: The regression was introduced (in 2018.3.0a4) along with the new Project Settings window. (Prior to that, "Script Execution Order" would appear in the Inspector window.)

Errors thrown:
- "MissingReferenceException: The object of type 'MonoScript' has been destroyed but you are still trying to access it. <...>"
- "ArgumentException: GUILayout: Mismatched LayoutGroup.repaint <...>"
- "GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced. <...>"
- "Scope was not disposed! You should use the 'using' keyword or manually call Dispose. <...>"