Mouse is no longer active?

I have a crosshair Gui that follows the mouse when the tool is equipped. But when I unequip it, the output says:

This mouse is no longer active

tool.Equipped:connect(function(mouse)

        print("Tool equipped!")

    -- Open Crosshair GUI       
        local gui = tool.CrosshairGUI
        local guiClone = gui:Clone()
        guiClone.Parent = player.PlayerGui

    -- Move Crosshair GUI to mouse position     
        local crosshairClone = guiClone:FindFirstChild("Crosshair")

        while wait() do
            local mousePosX = mouse.X -- It says this line is the problem
            local mousePosY = mouse.Y --  Same with this one
            crosshairClone.Position = UDim2.new(0, mousePosX - 25 , 0, mousePosY - 25)

            -- Hide mouse
            game:GetService("UserInputService").MouseIconEnabled = false

    tool.Unequipped:connect(function()

        -- Delete Crosshair GUI
        guiClone:Destroy()
        wait()

        -- Show mouse
        game:GetService("UserInputService").MouseIconEnabled = true
    end)