I have a bug in running code in Xcode (Thread 1: EXC_BAD_INSTRUCTION (code= EXC_I386+_INVOP, subcode=0x0)

Question

(Thread 1: EXC_BAD_INSTRUCTION (code= EXC_I386+_INVOP, subcode=0x0)

import Cocoa

class ViewController: NSViewController, NSSpeechRecognizerDelegate {

    @IBOutlet var output: NSTextView!
    var breakState = false

    var sr = NSSpeechRecognizer()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view
        sr!.delegate = self
        sr!.commands = ["Alpha", "Bravo", "Charlie", "Delta", "Echo", "Foxtrot", "Golf", "Hotel", "India", "Juliett", "Kilo", "Lima", "Mike", "November", "Oscar", "Papa", "Quebec", "Romeo", "Sierra", "Tnago", "Uniform", "Whiskey", "Xray", "Yanke", "Zulu", "space", "take a break", "get back to work"]
        sr!.startListening()
    }

    func speechRecognizer(_ sender: NSSpeechRecognizer, didRecognizeCommand command: String) {
        breakState = command == "take a break" ? true : command == "get back to work" ? false : breakState
        output.string! += !breakState && command != "get back to work" ? command == "space" ? " " : "\(command.characters.first!)" : ""
    }

    override var representedObject: Any? {
        didSet {
            // Update the view, if already loaded.
        }
    }
}