macOS Monterey Version 12.6
Firefox 108.0 (64-bit)
Unable to consistently reproduce, but the following error pops up when Nullboard is open in a background tab for a while (perhaps after computer sleeps then wakes up).
No part of this message is even remotely related to what's in the Nullboard code. I'd guess that this comes from (or induced by) one the add-ons that you have installed.
macOS Monterey Version 12.6 Firefox 108.0 (64-bit)
Unable to consistently reproduce, but the following error pops up when Nullboard is open in a background tab for a while (perhaps after computer sleeps then wakes up).