HeroModifiers will fail when a nested `when` modifier exist

```swift
view.heroModifiers = [
    .when({ $0.isMatched && $0.matchedView?.alpha != 0 && $0.view.alpha != 0 }, [
        .forceNonFade,
        .when({ ($0.isAppearing && $0.isPresenting || !$0.isAppearing && !$0.isPresenting) }, .opacity(0)),
    ]),
]
```

Look at this, `.opacity(0)` will never be added.