Block element button interactive on whitelisted pages

Environment

• Browser version: Chrome 83, haven't checked other browsers
• Extension version: ABP 3.8.4 (latest release), also can be reproduced on the latest version of ui-release-2019-4, haven't tried other versions
• Last working version: ?

Steps to reproduce

1. Navigate to http://example.com/test
2. Open the ABP popup and toggle the 'this page' toggle, to whitelist the page
3. Reload
4. Open the ABP popup again

Observed behavior

Block element button in the ABP popup is clickable.

Expected behavior

Block element button should be disabled on sites where adblocking is not active (the behavior should be the same as for whitelisted websites).

Hints for testers

• According to the spec, the button is expected to be hidden.
• The stats container should continue to be shown/hidden as expected.