can't load known-good lists in private browsing mode

[cardi]

If Firefox is in private browsing mode or its history setting is "Never remember history", AuntieTuna can't load any lists or interact with IndexedDB.

Console log:

[options] Error: InvalidStateError A mutation operation was attempted on a database that did not allow mutations.
 InvalidStateError: A mutation operation was attempted on a database that did not allow mutations.
options.js:13:35
     onError moz-extension://aefa24b5-5901-4fd6-8048-7dbe2c34e9d5/js/options.js:13

This is a known issue in Dexie.js: dexie/Dexie.js#883 and considered a bug in Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=781982

We could implement a workaround using WebExtension's local storage in place of IndexedDB, but the underlying logic as of now is reliant on Dexie.js handling the filters/joins on rows for us.