How to reproduce:
1. Open the attached “IN-128593” project
2. Open the “SampleScene”
3. In the Hierarchy window, select “UIDocument“
4. Enter Play mode
5. Exit Play mode
6. Observe the console
Actual result: Unity throws MissingReferenceException error
Expected result: No error messages in the Console window
Reproducible in: 6000.3.0b6 (211490bb75a6), 6000.3.3f1, 6000.4.0b3, 6000.5.0a4
Not reproducible with: 6000.0.65f1, 6000.3.0b5 (d8efd0de5abc)
Could not test with: 2023.1.0a1 (multiple package errors)
Reproducible on: Windows 11
Not reproducible on: No other environments tested