[LUA][ERROR] t.lib :55: attempt to index ? (a nil value)

--[[
		Main turtle utils

		x growh to left,
		y growh to up,
		z is height
		angle is anticlockwise, pi == 2, 0 is up
		and we allways start at 0,0,0,0
]]
moveMatrix = {
		{0,1}, -- up
		{1,0},  -- left
		{0,-1},  -- down
		{-1,0}  -- right
}

t = {} -- singleton

function t.init()
		t.x=0
		t.y=0
		t.z=0
		t.a=0
		t.m=moveMatrix[1]
end


function t.left()
		t.a=t.a+1
		t.a = t.a % 4
		t.m = moveMatrix[t.a+1] -- fucked lua table indexes
		turtle.turnLeft()
end
t.l = t.left


function t.right()
		t.a=t.a-1
		t.a = t.a % 4
		t.m = moveMatrix[t.a+1]
		turtle.turnRight()
end
t.r = t.right


function t.tryForward()
		if turtle.forward() then
				t.x = t.x + t.m[1]
				t.y = t.y + t.m[2]
				return true
		end
		return false
end
t.tf = t.tryForward


function t.digForward()
		repeat
				local _ = turtle.detect() and turtle.dig()
		until t.tryForward()
end
t.df = t.digForward


function t.tryUp()
		if turtle.up() then
				t.z = t.z + 1
				return true
		end
		return false
end
t.tu = t.tryUp


function t.digUp()
		repeat
				local _ = turtle.detectUp() and turtle.digUp()
		until t.tryUp()
end
t.du = t.digUp


function t.tryDown()
		if turtle.down() then
				t.z = t.z - 1
				return true
		end
		return false
end
t.td = t.tryDown


function t.digdown()
		repeat
				local _ = turtle.detectDown() and turtle.digDown()
		until t.tryDown()
end
t.dd = t.digdown


function t.faceTo(direction)
		local turnfunc = (direction > t.a) and t.l or t.r
		while(direction ~= t.a) do turnfunc() end
end
t.ft = t.faceTo


function t.hasSpace()
		return(turtle.getItemCount(9) == 0)
end
t.hs = t.hasSpace


function t.strCoord()
		return t.x .. ", " .. t.y .. " (" .. t.z .. ") a:" .. t.a
end

function t.getPos()
		return {x=t.x, y=t.y, z=t.z, a=t.a}
end

t.init()

common = {}

function common.dump(obj)
		print(obj,"n", textutils.serialize(obj))
end

--[[
		flatterns some space, dump mined at 0,0,0 facing down
		so, obsidian pipe must be at 0,-1,-1 and payload allways be safe
]]

local args = {...}
if #args == 0 then
		print("flatterrain <widthx> <widthy>")
		shell.exit()
end
local maxx,maxy = tonumber(args[1]), tonumber(args[2])

		

if not t then shell.run("t.lib") end
if not common then shell.run("common.lib") end
t.init()

local empty_levels = 0 -- levels without digging anything

function LOG(...) print(t.strCoord(), " ", ...) end


function ReturnToBase()
		while(t.z > 0) do t.dd() end
		t.ft(3)
		while(t.x > 0) do t.df() end
		t.ft(2)
		while(t.y > 0) do t.df() end
end


function GoToPosition(p)
		t.ft(0);
		while(t.y < p.y) do t.df() end
		t.ft(1)
		while(t.x < p.x) do t.df() end
		t.ft(p.a)
		while(t.z > p.z) do t.du() end
end


function DumpStomach()
		local i
		for i=1,9 do
				turtle.select(i)
				turtle.drop()
		end
		turtle.select(1)
end


function EmptyRun()
		local p = t.getPos()
		ReturnToBase()
		DumpStomach()
		GoToPosition(p)
end


t.df()
while(empty_levels < 3) do -- until there is only air
		for x=1, maxx do
				for y=2, maxy do -- alredy digged 1 block
						t.df()
						if not t.hs() then LOG("emptyRun"); EmptyRun(); end
				end
				local turnfunc = (x % 2 == 1) and t.l or t.r
				turnfunc(); t.df(); turnfunc()
		end
		local z = t.getPos().z
		if turtle.getItemCount(1) == 0 then empty_levels = empty_levels + 1 end
		ReturnToBase()
		DumpStomach()
		LOG("Level " .. z .." done");
		t.ft(0)
		for i=1,z+1 do t.du() end
		t.df()
end

ReturnToBase()


LOG("All done")