title: ARKit Project: Unexpectedly found nil while unwrapping an Optional value
body: <p>When I create an ArKit project on Xcode, the boilerplate project will not run and return an error that it cannot find the ship.scn asset.</p>
  <p>Boiler-plate code for the SceneKit project:</p>
  <pre><code>    import UIKit
      import SceneKit
      import ARKit
  
  class ViewController: UIViewController, ARSCNViewDelegate {
  
      @IBOutlet var sceneView: ARSCNView!
      
      override func viewDidLoad() {
          super.viewDidLoad()
          
          // Set the view's delegate
          sceneView.delegate = self
          
          // Show statistics such as fps and timing information
          sceneView.showsStatistics = true
          
          // Create a new scene
          let scene = SCNScene(named: &quot;art.scnassets/ship.scn&quot;)!
          
          // Set the scene to the view
          sceneView.scene = scene
      }
      
      override func viewWillAppear(_ animated: Bool) {
          super.viewWillAppear(animated)
          
          // Create a session configuration
          let configuration = ARWorldTrackingConfiguration()
  
          // Run the view's session
          sceneView.session.run(configuration)
      }
      
      override func viewWillDisappear(_ animated: Bool) {
          super.viewWillDisappear(animated)
          
          // Pause the view's session
          sceneView.session.pause()
      }
  
      // MARK: - ARSCNViewDelegate
      
  /*
      // Override to create and configure nodes for anchors added to the view's session.
      func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -&gt; SCNNode? {
          let node = SCNNode()
       
          return node
      }
  */
      
      func session(_ session: ARSession, didFailWithError error: Error) {
          // Present an error message to the user
          
      }
      
      func sessionWasInterrupted(_ session: ARSession) {
          // Inform the user that the session has been interrupted, for example, by presenting an overlay
          
      }
      
      func sessionInterruptionEnded(_ session: ARSession) {
          // Reset tracking and/or remove existing anchors if consistent tracking is required
          
      }
  }
  </code></pre>
  <p>Error: Fatal error: Unexpectedly found nil while unwrapping an Optional value: file</p>
  <p>Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value shows on following line:
  let scene = SCNScene(named: &quot;art.scnassets/ship.scn&quot;)!</p>
  <p>This was working for me previous to updating Xcode (current version is 13.0, Mac OS Big Sur Version 11.6).</p>
  <p>Wondering why this could be happening, and how to get around this?</p>