how to fix 15:44:29.596 ServerScriptService.BulletCreate:16: attempt to index nil?

help pls this is the parts of code that are important in this situation

local ServerStorage = game:GetService('ServerStorage')

remoteEvent.OnServerEvent:Connect(function(player, gunPos, mosPos)

    local bullet = Instance.new('Part')
    bullet.Name = "Bullet"
    bullet.Parent = game.Workspace
    bullet.Shape = Enum.PartType.Ball
    bullet.Size = Vector3.new(0.5, 0.25, 0.5)
    bullet.BrickColor = BrickColor.new("Gold")
    bullet.Orientation = Vector3.new(0, -90, 0)


    local damageScript = ServerStorage:FindFirstChild('Damage'):Clone()
    damageScript.Parent = bullet