Steps to reproduce:
1. Create and open a new project
2. Close project
3. Reopen project
4. Do not focus any window
5. Open Help->About Unity

Results: Incorrect window opens. If Editor's window is focused this issue won't be reproducible.

Reproduced with: 2020.1.0a12
Not reproducible with: 2019.3.0b10
Regression introduced in: 2020.1.0a6

Note:
- The issue is reproducible if the project is opened in corresponded Unity version. If project is upgraded, downgraded or a new project is created the issue won't be reproducible until reopened in the same Unity version.
- Reproducible with all Unity windows which can be opened from Toolbar.
- Reproduced in Windows 10. Not reproducible in OSX