I found my problem and solution. I made a custom theme based off persona and was using an old version of chats.js. I updated the chats.js file in my theme folder and the problem disappeared.
I don't see any problems there thought. Except for the bad value for main, it is supposed to be a javascript file; But since other NodeBB themes share this bad value it should not break anything. o_O
After a quick search with the search engine of my choice I've found this stackoverflow question with a similar issue. There doesn't seem to be a solution but moving your repo out of node_modules and either symlink (by hand; as the answer describes) or npm link it.
