How to reproduce:
1. Create a new project
2. Go to "Edit" -> "Project Settings" -> "Editor" and under "Version control" change the mode to "Perforce"
3. Go to "Help" -> "Check for updates"
4. Observe that no new window is opened

Expected result: a new update "Unity update check" window is opened
Actual result: no new window is opened and the "Help" dropdown is closed

Reproduced in: 2019.2.0b4, 2019.2.0a7
Not reproducible in: 2019.3.0a4, 2019.3.0a1, 2019.2.0a6, 2019.2.0a1, 2019.1.5f1, 2019.1.0a1, 2018.4.1f1, 2018.3.0a1, 2017.4.28f1, 2017.4.0f1

Note:
- This issue reproduced with any button under the "Help" dropdown, other dropdowns seem to be functioning properly. Changing the version control mode back to "Hidden Meta Files" won't fix the issue, only an editor restart fixes the button functionality.
- Additionally when switching back from Perforce the added Version Control menu in "Assets" -> "Version Control" is not removed