Reproduction steps:
1. Open attached project "1327051.zip"
2. Open Package Manager
3. Select "My Assets" in the second dropdown menu from the left side in the top-left corner of the Package Manager window
4. Close Package manager and open it again

Expected result: Errors do not appear in the Console after both the 3rd and 4th step
Actual result: Errors gets thrown and error gets printed out in the Console after both 3rd and 4th step

Reproducible with: Package Validation Suite 0.19.2-preview, 0.20.0-preview (2019.4.24f1, 2020.3.4f1, 2021.1.3f1, 2021.2.0a13)
Not reproducible with: Package Validation Suite 0.19.1-preview (2019.4.24f1, 2020.3.4f1, 2021.1.3f1, 2021.2.0a13)
Couldn't test with: 2018.4.34f1 (there is no "My Assets" window in Package Manager and error doesn't get printed out after the 4th step)

Notes:
- 2019.4.24f1, 2020.3.4f1 prints out another type of error:
[Package Manager Window] Package manager extension failed with error: Object reference not set to an instance of an object
UnityEditor.GenericMenu:CatchMenu (object,string[],int)
- 2019.4.24f1 doesn't print out an error after the 4th step