"Snooze!" button is wrongly hovered and clicked when time selection is in the past

[SoftVision-CarmenFat]

[Affected versions]:

• Release 58.0.2 and up
• Snooze Tabs 1.1.0

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a Firefox profile with the latest Snooze Tabs add-on version (https://github.com/bwinton/SnoozeTabs/releases/tag/1.1.0) loaded as a temporary add-on.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisite.
2. Navigate to a website (e.g. www.wikipedia.org) and click on the "SnoozedTabs" button.
3. Click the "Pick a Date/Time" option.
4. Hover the "Snooze!" button and observe what happens next.

[Expected result]:

• The "Snooze!" button is greyed out and cannot be hovered nor clicked.

[Actual result]:

• The "Snooze!" button enters a hover state where its background colors in a light grey and the white text is barely visible.

[Notes]:

• Attached a screen recording of the issue: