Lua Clean Specific Area Bug

[skywalker16]

I am trying to make an Area Clean on these cordinates but always receive lots of error messages, whether a tile is not used on the map ... (when no groundtile has been set on a cordinate)

Is there any way to make it like validate, whether there is a ground tile or not?

Error

[Error - GlobalEvent Interface]
In a time event called from:
data/globalevents/test_clean.luanTink
Description:
(luaDoCleanTile) Tile not found

Relevant Script Part

local CleanArenaArea = {
{x=1000, y=1000, z=6}, -- nw corner
{x=1020, y=1020, z=8} -- se corner
}


for x = (CleanArenaArea)[1].x, (CleanArenaArea)[2].x do
for y = (CleanArenaArea)[1].y, (CleanArenaArea)[2].y do
for z = (CleanArenaArea)[1].z, (CleanArenaArea)[2].z do
local clean_pos = {x = x, y = y, z = z}
if isCleanAbleArea(clean_pos) == true then
doCleanTile(clean_pos, false)
end
end
end
end