How do i fix this line of code? It is supposed to put your stand In front of you and punch

local combat = {}

function combat.Main(weld, Service, Stand, Anim, char, current)
	local info = TweenInfo.new(0.5)
	local goal = {}
	goal.C0 = weld.Part0.CFrame:ToObjectSpace(weld.Part1.CFrame)
	goal.C1 = weld.Part0.CFrame:ToObjectSpace(weld.Part1.CFrame * CFrame.new(0,0,-3))

	local tween = Service:Create(weld, info, goal)
	tween:Play()

	local Animation = Stand.AnimationController:LoadAnimation(Anim)
	Animation:Play()

	Animation.Stopped:Connect(function()
		local goal2 = {}

		goal2.C0 = weld.Part0.CFrame:ToObjectSpace(weld.Part1.CFrame)
		goal2.C1 = weld.Part0.CFrame:ToObjectSpace(weld.Part1.CFrame * CFrame.new(-3, 1.5, 3))

		local back = Service:Create(weld, info, goal2)
		back:Play()
	end)

	local hitbox = Instance.new("Part", Stand)
	hitbox.Anchored = false
	hitbox.CanCollide = false
	hitbox.Size = char.HumanoidRootPart.Size
	hitbox.CFrame = Stand.HumanoidRootPart.CFrame * CFrame.new(0, 0, -2.5)
	hitbox.Transparency = 1

	local hitboxWeld = Instance.new("ManualWeld")
	hitboxWeld.Name = "HitboxWeld"
	hitboxWeld.Part0 = hitbox
	hitboxWeld.Part1 = Stand.HumanoidRootPart
	hitboxWeld.C0 = hitbox.CFrame:ToObjectSpace(Stand.HumanoidRootPart.CFrame)
	hitboxWeld.Parent = weld.Part0

	hitbox.Touched:Connect(function(hit)
		if hit.Parent:FindFirstChild("Humanoid") then
			if not hit:IsDescendantOf(char) then
				local enemyHum = hit.Parent:FindFirstChild("Humanoid")

				if current == 3 then
					enemyHum:TakeDamage(5)
				else
					enemyHum:TakeDamage(2)
				end

				hitbox:Destroy()
			end
		end
	end)
end

Output:ServerScriptService.StandHandler.Combat:7: attempt to index nil with 'Part0'

I tried to local it or delete it but nothing works, any help would be great.

I think the Part0 of the weld wasn't set to any part. Have you set Part0 of the weld to any part before running the function?