Could not resolve a root view controller.

[trunghvbk]

Sometimes when I run the app, this runtime-warning happens, and I don't know why. I searched on the issue list and it seems no one has the same issue. Please help to check this. Thanks. The code of the Router is something like this

enum MainScreen {
    case pop
    case accountView
}

class MainRouter: UIViewControllerCoordinator<MainScreen> {
    override func transition(for route: MainScreen) -> ViewTransition {
        switch route {
        case .pop:
            return .dismiss
        case .accountView:
            return .push(AccountViewFactory(checkedUser: true))
        }
    }
}