Thank you! Now there's also SingleFileZ :)
More info here: https://addons.mozilla.org/firefox/addon/singlefilez

[UPDATED] This issue has been fixed in the version 1.9.79. I'm sorry for the inconvenience.

To people reading my response. Please don't report issues in the reviews. Technically speaking, we cannot have conversations here. Please contact me via the "Support Email" link (https://addons.mozilla.org/en-US/firefox/addon/single-file) or file an issue here: https://github.com/gildas-lormeau/SingleFile/issues. I'll do my best to fix your issue.