Reproduction steps:
1. Open the attached project “HDRBug”
2. In the project window, open “SampleScene”
3. In the hierarchy select the “Test” GameObject
4. In the inspector window inside “Test (Script)” open the “List” dropdown
5. Select a field in front of any element e.g. “Element 5” (“GameObject (5)”)
6. Press Backspace in an attempt to clear said field

Expected result: GameObject is removed from the field
Actual result: GameObject stays in the field

Reproducible with: 2022.2.0a17, 2022.2.16f1, 2023.1.0b9, 2023.2.0a8
Not reproducible with: 2020.3.47f1, 2021.3.22f1, 2022.2.0a16

Reproducible on: MacOS 12.2.1 (Intel)

Note: The field gets cleared out if you enter Play Mode or select some other object and come back to “Test”