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