I get SIGABRT error when hitting Fizz button in order to increment score if True

class ViewController: UIViewController {

    var score = 0
    var number = 1
    @IBOutlet weak var numberLabel: UILabel!
    @IBOutlet weak var scoreLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        scoreLabel.text = "Score \(score)"
        numberLabel.text = "\(number)"
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func fizzButton() {

        if fizzResult() == true { scoreLabel.text = "Score \(number + 1)" } else { print("nope") }
    }

    func fizzResult() -> Bool {
        if number % 3 == 0 { return true } else { return false }
    }
}