How to reproduce:
1. Create a new project
2. In the Project window create a new folder in Assets folder
3. Inside the created new folder create another folder
4. In the Project view expand the first created folder so it would show the subfolder
5. Delete the subfolder

Expected result: The icon of expanded folder returns to non expanded folder icon
Actual result: Folder icon stays on the expanded folder icon

Reproducible with: 2020.1.0a3, 2020.1.0b3, 2020.2.0a5
Could not test with: 2017.4.39f1, 2018.4.20f1, 2019.3.9f1, 2020.1.0a2 because the icon for expanded folder to show that it is expanded only appeared on 2020.1.0a3

Note: From version 2020.1.0a14 and later add a script inside the first created folder because the issue is reproduced only if after deleting the subfolder the first created folder does not become empty