Whenever I join Wynncraft with Wynntils or join a new world while using the mod, it opens the friends list immediately without me using the command /friends list. This also happens whenever I close the Wynntils settings menu.
I have joined Wynncraft in vanilla minecraft and it doesn't trigger and i even joined with 1.12 Wynntils and it never triggered, only when i used /friends list.

I have noted this, too. I think our FriendModel tries to list our friends, and try to hide the reply, but fails.