[SOLVED] [Lua] nested pairs() error

-- how many items to craft at once?
targetItemCount = 16
-- sleep time between inv checks
sleepTimeInventory = 2
-- which item from /craftingGrid/ to craft?
targetItemType = "compressedSawdust"

craftingGrid = {
	compressedSawdust = {
		true,	 true,	true,	false,
		true,	 false, true,	false,
		true,	 true,	true,	false,
		false,	 false,	false,	false
	}
}

craftingGrid_meta = {
	-- itemType = {
	--		resultSlot = number,
	-- }
}

function initCraftingGrid()
	for gridKey, gridValue in pairs(craftingGrid) do
		print(type(gridValue)) -- returns a table as it should
		local requiredCraftingSlots = 0
		-- that's the first slot where the items would go to
		local craftResultSlot
		
		-- line 30 throwing that error; it should iterate through table acquired by the previous pairs() function, e.g. craftingGrid[compressedSawdust]
		for slotKey, slotValue in pairs(gridValue) do -- line 30
			if slotValue then
				requiredCraftingSlots = requiredCraftingSlots + 1
			else
				if not craftResultSlot then
					craftResultSlot = slotKey
				end
				
				gridValue[ slotKey ] = nil	-- erase value from table
			end
		end
		
		if requiredCraftingSlots <= 9 then
			gridValue.craftingSlots = requiredCraftingSlots
		else
			print("Error: craftingGrid for [" .. gridKey .. "] requires more than 9 crafting slots!")
			print("Double-check this")
			error()
		end
		
		craftingGrid_meta[ gridKey ].resultSlot = craftResultSlot
		
		craftingGrid[ gridKey ] = gridValue -- apply changes to the global table from above
	end
end


function craftingGridSort( targetItem )
	local readyForCrafting = false
	
	for i, v in pairs( craftingGrid[ targetItem ] ) do
		
		-- item in slot /i/?
		if v then
		
			local currentSlotItems = turtle.getItemCount(i)
			
			-- return next slot or, if at the end, the first slot:
			local nextSlot = ( next(craftingGrid[ targetItem ], i) or next(craftingGrid[ targetItem ]) )
			
			if currentSlotItems > targetItemCount then
				turtle.select(i)
				turtle.transferTo(nextSlot, (currentSlotItems - targetItemCount))
			end
			
			if nextSlot == 1 then
				readyForCrafting = true
			end
		end
	end
	
	return readyForCrafting
end

function inputCraftingItems()
	-- fetch from craftingGrid table
	return turtle.suckUp()
end

function outputCraftedItems( targetItemType )
	-- same as above
	turtle.select( craftingGrid_meta[ targetItemType ].resultSlot )
	
	return turtle.dropDown()
end

-- runtime
initCraftingGrid()

while true do
	print("Iteration")
	turtle.select(1)
	
	while inputCraftingItems( targetItemType ) == false do
		-- no new input items
		sleep( sleepTimeInventory )
	end
	
	craftingGridSort( targetItemType )
	turtle.craft()
	
	while outputCraftedItems( targetItemType ) == false do
		print("Can't output crafted Items!")
		sleep(5)
	end
	
	sleep( sleepTimeInventory )
end

craftingGrid = {
	compressedSawdust = {
		true,	 true,	true,	false,
		true,	 false, true,	false,
		true,	 true,	true,	false,
		false,	 false,	false,	false
	}
}

function initCraftingGrid()
	for gridKey, gridValue in pairs(craftingGrid) do
		print(type(gridValue))
		local requiredCraftingSlots = 0
		-- that's the first slot where the items would go to
		local craftResultSlot
		
		for slotKey, slotValue in pairs(gridValue) do
			if slotValue then
				requiredCraftingSlots = requiredCraftingSlots + 1
			else
				if not craftResultSlot then
					craftResultSlot = slotKey
				end
				
				gridValue[ slotKey ] = nil	-- erase value from table
			end
		end
	end
end
initCraftingGrid()