How to reproduce:
1. Open the user's attached project
2. In the Project window select Scripts > NewAssembly
3. In the Inspector check the "Allow 'unsafe' Code" checkbox
4. In the Project window select NewBehaviourScript
5. In the Unapplied import settings pop-up select "Apply"
6. Reselect the NewAssembly and observe the Inspector

Expected result: The "Allow 'unsafe' Code" checkbox is checked
Actual result: The "Allow 'unsafe' Code" checkbox is not checked

Reproducible with: 2019.4.15f1, 2019.4.21f1, 2020.1.4f1, 2020.1.17f1, 2020.2.0a21, 2020.2.6f1, 2021.1.0b8, 2021.2.0a7
Not reproducible with: 2018.4.32f1, 2019.4.14f1, 2020.2.0a20, 2020.1.3f1

Notes:
- The issue is reproducible on Mac
- The issue is not reproducible on Windows
- This affects all Assembly Definition settings
- The issue doesn't reproduce when pressing the Apply button in the Inspector