How to reproduce:
1. Open attached project "Matchbox_trunk.zip"
2. Delete "GameLoadClass.cs" in the project
3. Build the project
4. Launch the build
5. Exit the build opened
6. Launch the build again
Expected result: Build does not crash
Actual result: Build crashes
Reproducible with - 2019.4.28f1, 2020.3.12f1, 2021.1.12f1, 2021.2.0a21