Hello,

Corrupted database error is a Firefox bug, and very old one (4 years old): https://bugzilla.mozilla.org/show_bug.cgi?id=944918

There are cases where this happened after running CCleaner or other tools that can "optimize" or "compact" Firefox database. But it can also happen if you start any Firefox with version older that 57 - your profile get instantly corrupted (once your profile get upgraded with Firefox 57 and newer, it cannot be downgraded).

To validate status of your database engine you can visit this demo page:
http://mdn.github.io/to-do-notifications/
This page is using same database technology as my add-on. Check the log text in bottom left corner - if you see there "Error loading database" then your Firefox has indeed broken database.

What will help is Firefox reset feature:
https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings
Resetting profile will preserve your passwords, bookmarks and other important things.

I'm really sorry for the inconveniences...

Have a nice day and enjoy the weekend :)

Best regards,
Juraj Mäsiar