invalid argument #2 (Vector3 expected, got nil) I'm getting this how to I fix it?

local rp = game:GetService("ReplicatedStorage")
local Sword = rp:WaitForChild("Sword")

local cframes = {
	["Right Arm"] = CFrame.new(0,-1,0),
	["Right Hand"] = CFrame.new(0,0,0)
}

Sword.OnServerEvent:Connect(function(Player,isEquipped)
	local Character = Player.Character
	local Humanoid = Character.Humanoid

	if isEquipped then
		--Equipping the sword
		local Katana = Character:FindFirstChild("Katana")
		if Katana then
			local SideWeld = Katana.PrimaryPart:FindFirstChild("SideWeld")
			if SideWeld then
				SideWeld:Destroy()

				if Humanoid.RigType == Enum.HumanoidRigType.R15 then
					Katana:SetPrimaryPartCFrame(Character:WaitForChild("RightHand").CFrame * cframes.RightHand)
				elseif Humanoid.RigType == Enum.HumanoidRigType.R6 then
					Katana:SetPrimaryPartCFrame(Character:WaitForChild("Right Arm").CFrame * cframes["Right Arm"])

				end

				local HandWeld = Instance.new("ManualWeld")
				HandWeld.Part0 = Katana.PrimaryPart

				if Humanoid.RigType == Enum.HumanoidRigType.R15 then
					HandWeld.Part1 = Character:WaitForChild("Righthand") -- this is the errored line
				elseif Humanoid.RigType == Enum.HumanoidRigType.R6 then
					HandWeld.Part1 = Character:WaitForChild("Right Arm")
				end

				HandWeld.C0 = > HandWeld.Part0.CFrame:ToObjectSpace(HandWeld.Part1.CFrame)
				HandWeld.Parent = HandWeld.Part0

			end
		end
	elseif not isEquipped then
		--Unequipping the sword


	end

end)

Note: This problem only happens in R15 and I want the game to be compatible with both R15 and R6