[Lua][Error] minenow:111: attempt to index ? (a nil value)

function invClear()
  turtle.select(16)
  while not turtle.placeUp() do
	turtle.digUp()
  end
  for i = 1, 14 do
	turtle.select(i)
	turtle.dropUp()
  end
  turtle.select(16)
  turtle.digUp()
end
function refuel(x)
  if x > turtle.getFuelLevel() then
	invClear()
	turtle.select(15)
	while not turtle.placeUp() do
	  turtle.digUp()
	end
	end
  while x > turtle.getFuelLevel() do
	turtle.suckUp()
	turtle.refuel()
  end
  turtle.select(15)
  turtle.digUp()
end
function mine(x)
  refuel(x + 10)
  for i = 1, x do
	if turtle.getItemCount(12) > 0 then
	  invClear()
	end
	while not turtle.forward() do
	  turtle.dig()
	end
	while turtle.detectUp() do
	  turtle.digUp()
	end
	turtle.digDown()
  end
end

function turn()
  if Richtung == "r" then
	turtle.turnRight()
	mine(1)
	turtle.turnRight()
	Richtung = "l"
  else
	turtle.turnLeft()
	mine(1)
	turtle.turnLeft()
	Richtung = "r"
  end
end
function calcx()
  if (mgox - mendx) >= 0 then
	return mgox - mendx
  else
	return mendx - mgox
  end
end
function calcy()
  if (mgoy - mendy) >= 0 then
	return mgoy - mendy
  else
	return mendy - mgoy
  end
end
function calcz()
  if (mgoz - mendz) >= 0 then
	return mgoz - mendz
  else
	return mendz - mgoz
  end
end
function calcstart()
  rednet.open("right")
  cx, cy, cz = gps.locate(3)
  if (mgox - cx) >= 0 then
	x = mgox - cx
  else
	x = cx - mgox
  end
  if (mgoy - cy) >= 0 then
	y = mgoy - cy
  else
	y = cy - mgoy
  end
  if (mgoz - cz) >= 0 then
	z = mgoz - cz
  else
	z = cz - mgoz
  end
  return x + y + z + 200
end

function getvariables()
  cx, cy, cz = gps.locate(3)
  mnx = mgox
  mnz = cz

  file = fs.open("y", "r")
  mny = file.readLine()
  file.close()
  mny = mny + 0

  file = fs.open("end", "r")
  ended = file.readLine()
  file.close()
  ended = ended + 0
end
function start()
  if turtle.getItemCount(16) > 0 then
	refuel(calcstart())
	shell.run("goto", mgox, mgoy + 2, mgoz, "1")
	turtle.select(13)
	turtle.transferTo(16, 1)
  else
	refuel(calcx + calcz + 50)
	shell.run("goto", mnx, mny + 2, mnz, "1")
  end
  for i = 1, 2 do
	while not turtle.down() do
	  turtle.digDown()
	end
  end
end
function debug()
  if turtle.getItemCount(16) > 0 then
	turtle.select(15)
	turtle.digUp()
  elseif turtle.getItemCount(13) > 0 then
  else
	turtle.select(16)
	turtle.digUp()
  end
end
function nexty(x)
  mny = mny - x
  file = fs.open("y", "w")
  file.writeLine(mny)
  file.close()
end
function newy()
  cx, cy, cz = gps.locate()
  if cy - 4 >= mendy then
	nexty(3)
  elseif cy - 3 == mendy then
	nexty(2)
  elseif cy - 2 == mendy then
	nexty(1)
  else
	file = fs.open("end", "w")
	file.writeLine(1)
	file.close()
  end
end
function back()
  invClear()
  turtle.select(16)
  turtle.transferTo(13, 1)
  start()
  turtle.up()
  turtle.up()
end
function chegz()
  cx, cy, cz = gps.locate(3)
  if mendz - cz ~= 0 then
	return true
  else
	return false
  end
end
function createfile()
  file = fs.open("y", "r")
  if file.readLine() then
  else
	file.close()
	file = fs.open("y", "w")
	file.writeLine(mgoy)
	file.close()
  end
  file = fs.open("end", "r")
  if file.readLine() then
  else
	file.close()
	file = fs.open("end", "w")
	file.writeLine(0)
	file.close()
  end
end

mgox  = -145
mendx = -135
mgoy  = 240
mendy = 230
mgoz  = 77
mendz = 67
Richtung = "r"
os.loadAPI("mine")
debug()
getvariables()
while ended == 0 do
start()
while chegz() do
mine(calcx())
turn()
end
mine(calcx())
newy()
getvariables()
end
back()

local ziel = {...}
local zx = ziel[1]
local zy = ziel[2]
local zz = ziel[3]
local zdirect = ziel[4]
zx = zx +0
zy = zy +0
zz = zz +0
zdirect = zdirect +0

rednet.open("right")
local fx, fy, fz = gps.locate(3)
for i = 1, 4 do
if turtle.forward() then
sx, sy, sz = gps.locate(3)
direct = nil
if fz < sz then
  direct = 0
elseif fz > sz then
  direct = 2
elseif fx > sx then
  direct = 1
elseif fx < sx then
  direct = 3
end
break
else
turtle.turnRight()
end
end
function turn(ndirect)
  while ndirect ~= direct do
	turtle.turnRight()
	if direct ~= 3 then
	  direct = direct + 1
	else
	  direct = 0
	end
  end
end
if direct ~= nil then
local fail = 0
function z0()
  if zz > sz then
	turn(0)
	if turtle.forward() then
	  sz = sz + 1
	  fail = 0
	  z0()
	else
	  x1()
	end
  else
	x1()
  end
end
function x1()
  if zx < sx then
	turn(1)
	if turtle.forward() then
	  sx = sx - 1
	  fail = 0
	  x1()
	else
	  z2()
	end
  else
	z2()
  end
end
function z2()
  if zz < sz then
	turn(2)
	if turtle.forward() then
	  sz = sz - 1
	  fail = 0
	  z2()
	else
	  x3()
	end
  else
	x3()
  end
end
function x3()
  if zx > sx then
	turn(3)
	if turtle.forward() then
	  sx = sx + 1
	  fail = 0
	  x3()
	else
	  yu()
	end
  else
	yu()
  end
end
function yu()
  if fail ~= 1 then
  if zy > sy then
	if turtle.up() then
	  sy = sy + 1
	  fail = 0
	  yu()
	else
	  yd()
	end
  else
	yd()
  end
  elseif zy ~= sy then
  else
	turtle.up()
	sy = sy + 1
	z0()
  end  
end
function yd()
  if zy < sy then
	if turtle.down() then
	  sy = sy - 1
	  fail = 0
	  yd()
	else
	  cheg()
	end
  else
	cheg()
  end
end
function cheg()
  if fail == 1 then
  if zx == sx then
	if zy == sy then
	  if zz == sz then
		print("Ich bin angekommen und schalte ab!")
	  else
		print("fail")
	  end
	else
	  print("fail")  
	end
  else
	print("fail")
  end
  else
	if fail == 0 then
	  if zx == sx then
		if zy == sy then
		  if zz == sz then
			print("Ich bin angekommen und schalte ab!")
		  else
			fail = 1
			z0()
		  end
		else
		  fail = 1
		  z0()
		end
	  else
		fail = 1
		z0()
	  end
	end
  end
end
z0()
turn(zdirect)
else
print("I need space arround me!")
end