So has anyone come up with a simple way to fix this? if so can anyone give me instructions on how to fix it. thanks

I went to play through the campaign, once i got through the first part of it it came up this message: Unknown key:"Error while running the oninit: ...Data\Roaming\Factorio\temp\currently-playing\control.lua:39: attempt to index field 'wall' (a nil value)" I don't know what caused it but no...