The "Delete" button wrongly remains focused after cancelling the "Delete this Entry?" pop-up

[SoftVision-CosminMuntean]

[Affected Versions]:

• Lockbox 2.1.0-alpha
• Firefox 66.0.3 and up

[Affected Platforms]

• All Windows
• All Linux

[Perquisites]

• Have the latest Firefox 66.0.2 installed.
• Have a Firefox profile with the "xpinstall.signatures.dev-root" pref created and set to "true".
• Have the Lockbox 2.1.0 - alpha extension instaled.
• Have multiple logins saved.

[Steps to reproduce]:

1. Open the Firefox browser with the profile from prerequisites.
2. Click on the Lockbox tollbar button.
3. Click the "Open Lockbox" button from the displayed doorhanger.
4. Click any of the saved logins from the list.
5. Click the "Delete" button from the top right corner of the page.
6. Click the "Cancel" button from the displayed pop-up.
7. Observe the "Delete" button.

[Expected results]:

• The "Delete" button is not focused.

[Actual results]:

• The "Delete" button is focused.

[Notes]:

• The issue is not reproducible on Mac OSes.
• Attached a screen recording with the issue: