So, I searched for previous issues prior to creating this and found issue #2120. This is a duplicate of my issue, and I'm currently using LuckPerms 5.0.72, which I believe is older than the c3128de commit you mentioned in that issue.

Proof of being a duplicate:

My question is this - how do I go about using this commit? I've never learned how to compile a jarfile from GitHub, and before digging into that, I want to be certain of what exactly I'm supposed to do to use this edit you made.

Minor edit:
Apparently despite throwing an error, LuckPerms still correctly assigned permissions:

Does this mean I have nothing to be concerned about? Or are there issues which may occur that still require me to use the commit you made?

https://luckperms.net/ for downloads.

https://luckperms.net/ for downloads.

Huh. Well, today I learned LuckPerms has a dedicated website and Jenkins. I've only ever been aware of the GitHub and Spigot page. Thank you, @BrainStone.

I'll test the latest dev build (5.0.128) and see if it resolves the issue.

Okay, updating from 5.0.72 to 5.0.128 resolved this issue. Thank you again, @BrainStone.