Good afternoon! Please tell me how to load the usdz model from the url link (https) in AR Quick Look, I am using the code from the listing of the Apple presentation, and I get an error "Fatal error: Unexpectedly found nil while unwrapping an Optional value", what am I doing wrong? I hope and really look forward to your reply. The application compiles correctly, the error occurs after pressing a button on the device itself. import UIKit import QuickLook import ARKit import RealityKit class ViewController: UIViewController, QLPreviewControllerDataSource {   override func viewDidLoad() {     super.viewDidLoad()   }   @IBAction func startDecoratingButtonPressed(_ sender: Any) {     let previewController = QLPreviewController()     previewController.dataSource = self     present(previewController, animated: true, completion: nil)   }   func numberOfPreviewItems(in controller: QLPreviewController) -> Int { return 1 }       func previewController(_ controller: QLPreviewController, previewItemAt index: Int) -> QLPreviewItem {     let fileUrl = Bundle.main.url(forResource: "toy_drummer", withExtension: "usdz")!     let previewItem = ARQuickLookPreviewItem(fileAt: fileUrl)     previewItem.canonicalWebPageURL = URL(string: "https://developer.apple.com/augmented-reality/quick-look/models/drummertoy/")     previewItem.allowsContentScaling = false     return previewItem   } }