Unable to cast token to token

Help and Feedback Scripting Support
#1

Getting error: Unable to cast token to token

Heres the script:

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()
local UIS = game:GetService("UserInputService")

local target = nil
local isholdingdown = false

UIS.InputChanged:Connect(function(input)
	if UIS:IsKeyDown(Enum.UserInputType.MouseButton1) == true then --Error on this line
		isholdingdown = true
		game.ReplicatedStorage.CreatePart:FireServer(target, mouse.Hit.Position, isholdingdown)
	elseif UIS:IsKeyDown(Enum.UserInputType.MouseButton1) == false then
		isholdingdown = false
		game.ReplicatedStorage.CreatePart:FireServer(target, mouse.Hit.Position, isholdingdown)
	end
end)

mouse.Move:Connect(function()
	target = mouse.Target
	if not target then
		mouse.Icon = 'http://www.roblox.com/asset/?id=591711615'
	else
		if target:IsA("BasePart") or target:IsA("Model") then
			if target == workspace.Base or target == workspace.Base2 or target.Parent == workspace.Map then 
				mouse.Icon = 'http://www.roblox.com/asset/?id=6888146193'
			else
				mouse.Icon = 'http://www.roblox.com/asset/?id=591711615' 
			end
		end
	end
end)