https://forums.factorio.com/viewtopic.php?f=95&t=43759

I found the problem, in Flare Stack's mod : In file data-final-fixes.lua line 94

if not (vi.fuel_category and vi.fuel_category == "chemical"
and not fuelGreaterThan(coal_value, vi.fuel_value)) then

When threating the following recipe :

{
  flags = {
    "goes-to-main-inventory"
  },
  fuel_category = "chemical",
  icon = "__angelspetrochem__/graphics/icons/coal-crushed.png",
  name = "coal-crushed",
  order = "a[carbon]",
  stack_size = 200,
  subgroup = "petrochem-raw",
  type = "item"
}

Since the recipe don't have a fuel value, when calling fuelGreaterThan(coal_value, vi.fuel_value), the second parameter is nil.

Then is the same file, line 44

  local exp2 = fuel_suffix_list[string.sub(fuel2,string.find(fuel2, "%a+"))]

when fuel2 is nil, it throw an error because it should be a string.

I think that a parameter should be checked or before calling the function actually check that it have a fuel value before assuming so.

I see, coal-crushed. SeaBlock removes the fuel_value from that item (also from wood-bricks). I forgot about fuel_category, it's probably a bad idea to leave items with partial fuel properties set though. The next release of SeaBlock will remove fuel_category as well.

EDIT: Update released, should be working with SeaBlock_0.1.10

I've updated to fix this bug. Please remember that these comment sections don't alert me when people post, whereas the forums email me when someone posts in my threads.