My NPC's pathfinding script is not working, so how do I fix the problem?

I made a script for an NPC where it walks from one point to another in a while loop, but if it sees a player it goes after them. I tried moving some things around to see if it works. I also get an error saying "Workspace.Guard.Script:28: attempt to index nil with 'Parent'". I need help finding out what is wrong in the script.

Script:

local firstpoint = workspace.pointforguard.Position
local secondpoint = workspace.pointforguard1.Position
local hum = script.Parent:WaitForChild("Humanoid")
local hrp = script.Parent:WaitForChild("HumanoidRootPart")
local model = script.Parent
local player = game.Players.LocalPlayer
local hum = script.Parent:WaitForChild("Humanoid")
local t = script.Parent:WaitForChild("UpperTorso")
local pfs = game:GetService("PathfindingService")


model.PrimaryPart = hrp

while true do
	wait(2)
		hum:MoveTo(firstpoint)
			hum.MoveToFinished:Wait()
				model:SetPrimaryPartCFrame(hrp.CFrame * CFrame.Angles(0,math.rad(180), 0))
					wait(15)
			hum:MoveTo(secondpoint)
		hum.MoveToFinished:Wait()
	wait(15)
	function getTarget()
		target = nil
		for i, v in pairs(game.Workspace:GetChildren()) do
		    human = v:FindFirstChild("Humanoid")
		    torso = v:FindFirstChild("LowerTorso")
			if human.Parent and torso.Parent == player.Character then
				target = torso
				break
			end
		end
	end
	if target == torso then
		while wait() do
			local torso = getTarget()
			if torso then
				local path = pfs:CreatePath()
				path:ComputeASync()
				local waypoint = path:GetWaypoints()
				for i, waypoint in pairs(waypoint) do
					human:MoveTo(torso.Position)
					human.MoveToFinished:Wait(2)
				end
			end
		end
	else
		return target
	end
end

The LowerTorso has a potential to be nil (player died). You need to account for that case by first checking if the part even exists.

if torso then
	if human.Parent and torso.Parent == player.Character then
	    target = torso
	    break
	end
end

It is also worth mentioning :Wait() takes no arguments (the 2 does nothing there.) MoveToFinished will end when the engine has determined the goal was reached, or timeout after 8 seconds if the humanoid seems stuck.