Model:SetPrimaryPartCFrame() failed because no PrimaryPart has been set how do i fix this?

This is My code

local Case = script.Case:Clone()game.Players.PlayerAdded:Connect(function(Player)
	Player.CharacterAdded:Connect(function(Character)
		local Case = script.Case:Clone()
	    Case:SetPrimaryPartCFrame(Character.HumanoidRootPart.CFrame)
		Case.Parent = Character
		
		
		local weld = Instance.new("ManualWeld")
		weld.Part0 = Case.PrimaryPart
		weld.Part1 = Character.PrimaryPart
		weld.C0 = weld.Part0.CFrame:ToObjectSpace(weld.Part1.CFrame)
		weld.Parent = weld.Part0
		
	end)
end)
--ERROR ON LINE 4

someone Please tell me how to fix this this was in a katana tutorial by RED plys if that helps.