Unable to close filter suggestion window in Block Element

Environment

• OS version: macOS 10.15
• Browser version: Opera (older and latest versions)
• Extension version: Reproducible in ABP 3.8 and dev builds for ABP 3.9
• Last working version: NA

Steps to reproduce

1. On Opera, open any website and Click "Block Element" in the Pop-up UI
2. Try blocking an element on the page
3. Click the "Add" or "Cancel" buttons in the filter suggestion window

Observed behavior

The filter suggestion window remains open after clicking the "Add" or "Cancel" button

Expected behavior

The filter suggestion window should be closed after clicking the "Add" or "Cancel" button

Further information

• This only happens in Opera. Other browsers show the expected behavior.
• With the latest changes in 2019-4: https://gitlab.com/eyeo/adblockplus/abpui/adblockplusui/-/issues/761 and https://gitlab.com/eyeo/adblockplus/abpui/adblockplusui/-/issues/638, clicking the Unselect in the filter's suggestion window has the same issue, causing the composer windows to pile up with each user's selection