It's just a warning. Maybe if you pack the mod and activate in the mod menu, it will work. Can't remember where you have to put the packed file. Documents or something. Never got that quite working myself. Hopefully you can activate that in mid-game. Folder in the game data folder works well enough for me. Error is a just an extra box to tick. Only a bit annoying when you're closing and reopening the game to check your changes over and over again.
