Open Radar

 
When creating multiple nested `NavigationLink`s where the final destination is a `UIViewControllerRepresentable`, the destination will only be shown on the first try. On subsequent tries, it will load a blank screen.

# System

iPhone 11 Pro Simulator, 14.5, Xcode 12.5 (12E262)
Also: iPhone 11 Pro running iOS 14.7.1

# Steps to Reproduce

* Use the following code in a basic SwiftUI app:

```swift
class HelloWorldVC: UIViewController {
    override func loadView() {
        super.loadView()
        let label = UILabel()
        label.text = "Hello, World"
        view.addSubview(label)

        label.translatesAutoresizingMaskIntoConstraints = false
        label.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor).isActive = true
        label.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor).isActive = true
        label.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor).isActive = true
        label.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
    }
}

struct ViewControllerContainer: UIViewControllerRepresentable {
    let vc: UIViewController

    func makeUIViewController(context: Context) -> some UIViewController { vc }
    func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {}
}

struct ContentView: View {
    var body: some View {
        NavigationView {

            // Works:
            //NavigationLink("View UIKit VC", destination: ViewControllerContainer(vc: HelloWorldVC()))

            // Only loads the UIKit view once. It's blank on subsequent tries.
            NavigationLink(
                "Detail Screen",
                destination: NavigationLink(
                    "View UIKit VC",
                    destination: ViewControllerContainer(vc: HelloWorldVC())
                )
            )
        }
    }
}
```

* Tap "Detail Screen"
* Tap "View UIKit VC". You will see the "Hello, World" UIViewController.
* Tap Back
* Tap "View UIKit VC"

Expected: 
* You should see the "Hello, World" UIViewController again

Actual:
* You will see a blank view. This will happen as many times as you try.

This is unexpected and will cause accessibility users confusion.

Screenshot:

![Video of bug](https://github.com/jgale/NavigationLinkUIVCRBug/blob/main/navigation_link_bug.mov)