Existing livemarks not updated, can't add it again from different address

[mrmangas]

Add-on version
Add-on version: 3.8
Firefox version: 134.0

Describe the bug
Due to recent changes in feedburner, one of my favorite sites had to change the address of its RSS feeds. Unfortunately, Livemarks (and most other add-ons of this type for Firefox) fails to save the new address of the feeds, returning an error.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'https://satkurier.pl/magazyn/10/rss'
2. Click on any link, e.g. https://satkurier.pl/rssfeed/polskieplatformy
3. Site is loaded, but Livemarks is not starting to subscribe.
4. When I add it manually in options menu, I got empty folder, with no feeds.

Expected behavior
A clear and concise description of what you expected to happen.

Extra context
Any extra context you may have about the bug (feed URLs, screenshots, etc.)