On this part of code something is missing

func deleteSelected() {
        guard let selectedReview = dataController.selectedReview else { return }
        guard let selectedIndex = reviews.firstIndex(of: selectedReview) else { return }
        managedObjectContext.delete(selectedReview)
        dataController.save()

        if selectedIndex < reviews.count {
            dataController.selectedReview = reviews [selectedIndex]
        } else {
            let previousIndex = selectedIndex - 1
            if previousIndex >= 0 {
                dataController.selectedReview = reviews[previousIndex]
            } else {
                dataController.selectedReview = nil // This line is missing in th book
            }
        }
}

In my point of view you have to set selectedReview to nil to display Text("Please select a review") in ContentView. You can check my personnal project and tell me your point of view.

https://github.com/Sebastien-Remy/hackingWithmacOS-16-Bookworm