How can I fix the zombie? also how can I add It so the zombie damages other players, but not you?

Im making a zombie staff that summons a zombie that acts like a guard dog, the zombie will attack other players besides you, anyway the problem Is where the zombie won't move, the output says:

Argument 2 missing or nil

I was wondering why, also I was wondering how can I modify the script so It damages other players besides you

Also there Is a StringValue In the zombie, the reason why It Is there Is because of the spawning script which can be found below the pathfinding

PathFinding:

local NPC = script.Parent
local Pathfinding = game:GetService("PathfindingService")
local Creator = script.Parent.Creator
function GetPlayerNames()
	local players = game:GetService('Players'):GetChildren()
	local name = nil
	for _, v in pairs(players) do
		if v:IsA'Player' then
			name = tostring(v.Name)
		end
	end
	return name
end
function GetTorso(part)
	local chars = game.Workspace:GetChildren()
	local torso = nil
	for _, v in pairs(chars) do
		if v:IsA'Model' and v ~= script.Parent and v.Name == GetPlayerNames() and not v.Name == Creator.Value then
			local charRoot = v:FindFirstChild'HumanoidRootPart'
			if (charRoot.Position - part).magnitude < SearchDistance then
				torso = charRoot
			end
		end
	end
	return torso
end
while task.wait() do
	local path = Pathfinding:CreatePath()

	path:ComputeAsync(NPC.Torso.Position, GetTorso(NPC.Torso.Position))--its gonna make a radius around the npc torso position to check for players

	if path.Status == Enum.PathStatus.Success then

		local Positions = path:GetWaypoints()

		for i,v in pairs(Positions) do

			local position = Instance.new("Part")

			position.Parent = game.Workspace

			position.Size = Vector3.new(1,1,1)

			position.Position = v.Position

			position.Transparency = 1

			NPC.Humanoid:MoveTo(position.Position)

			NPC.Humanoid.MoveToFinished:Wait(2)

			position:Destroy()

		end

	end
end

Summon script:

local tool = script.Parent
local debounce = false

tool.Activated:Connect(function()
	if not debounce then
		debounce = true
		local Zombie = game.ReplicatedStorage.Zombie:Clone()
		Zombie.Parent = game.Workspace
		Zombie.Torso.CFrame = tool.Handle.CFrame
		if Zombie:FindFirstChild("Creator") then
			Zombie:FindFirstChild("Creator").Value = tool.Parent.Name --Tool > Character > Name
		end
	end
end)

Too hard. Always got it not working. ------- OLD POST --------------- First fix Line 30 to this:

-- Lines before Line 30
local NPC_Torso
if NPC:FindFirstChild("UpperTorso") then
	NPC_Torso = NPC.UpperTorso
else
	NPC_Torso = NPC.Torso
end
if GetTorso(NPC_Torso) == nil then
	return
end
-- Line 30
path:ComputeAsync(GetTorso(NPC_Torso).Position, GetTorso(NPC_Torso).Position)--its gonna make a radius around the npc torso position to check for players

I'm really confused!

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