When using https://mods.factorio.com/mod/RemoveBiterSoil I get the following error:

Error while running event ChunkyChunks::on_tick (ID 0)
ChunkyChunks/control.lua:357: attempt to index local 'surface' (a nil value)
stack traceback:
ChunkyChunks/control.lua:357: in function 'iterate_surface_chunks'
ChunkyChunks/control.lua:235: in function <ChunkyChunks/control.lua:217>

I solved it for now by adding a check for nil in control.lua:

function iterate_surface_chunks(surface)
local c = 0
if not (surface == nil) then
for chunk in surface.get_chunks() do
c = c + 1
blockify({position = fromXY(chunk), surface = surface})
end
end
return c
end

No idea of the implications, but now It does not crash at least.

I have the same problem in a EditorExtension save, I resolved it with checking for nil in the on_tick function:

    if empty and game.surfaces[index] then iterate_surface_chunks(game.surfaces[index]) end

Seems not to happen often since I'm not sure what triggered it as I used EditorExtensions before very often. Maybe because I copied some terrain in Editor mode. Fixing it this way does not seem to have any negative impact.

May Qon will return with the expansion, maybe someone will fork it ;-)

Thanks for the report!
I do read my notifications sometimes even if I'm not actively playing/modding the game right now.
But I have some vacation time now so there's at least a tiny chance I'll get back to fixing stuff before the DLC.

Thats great, thanks for responding!