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I created a new macOS GUI App. Add a notification observer to UserDefaults.didChangeNotification in ViewController.swift.

I will get one notification when the app starts, one when I click the window that contains the ViewController. 

However, in my opinion, the `UserDefaults.didChangeNotification` shouldn't fire as nothing is changed.

Steps to Reproduce:
1. open the attached project and run.
Or
1. create a new macOS GUI app
2. add below code to ViewController and run

class ViewController: NSViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        NotificationCenter.default.addObserver(self, selector: #selector(userDefaultsDidChange), name: UserDefaults.didChangeNotification, object: nil)
    }
    
    override func viewWillDisappear() {
        super.viewWillDisappear()
        
        NotificationCenter.default.removeObserver(self, name: UserDefaults.didChangeNotification, object: nil)
    }

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

    func userDefaultsDidChange() {
        print("user defaults did change.")
    }
}