The Notes three dot menu is not closed when clicking outside the notes sidebar

[Softvision-RemusDranca]

[Affected versions]:

• Firefox 60.0.2 and above

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a new Firefox profile with the latest version of "Firefox Notes" add-on (4.2.0 RC2) installed.
• Have the Notes opened in note view.

[Steps to reproduce]:

1. Click the three dot menu button to have the menu open.
2. Click outside the Firefox Notes sidebar.
3. Observe the Notes three dot menu.

[Expected result]:

• The menu is closed.

[Actual result]:

• The menu is not closed.

[Notes]:

• This issue is also reproducible with the sync menu.
• This issue is also reproducible with the TxP version of Firefox Notes.
• This issue is not reproducible when clicking inside the notes sidebar.
• This issue is also reproducible when clicking the Sidebar switcher.
• Attached is a screen recording of the issue: