title: Swift - Google Map crashes with 'unexpectedly found nil' error
body: <p>I am trying to set a <code>GoogleMap</code> to a <code>UIView</code> and add it as a Subview. However, when running the app I get this error:</p>
  
  <blockquote>
    <p>fatal error: unexpectedly found nil while unwrapping an Optional value</p>
  </blockquote>
  
  <p>It crashes at code line:</p>
  
  <pre><code>mapView.camera = camera
  </code></pre>
  
  <p><strong>Here's my full ViewController code:</strong></p>
  
  <pre><code>class LocationViewController: UIViewController {
      @IBOutlet weak var mapView: GMSMapView!
  
      override func viewDidLoad() {
          super.viewDidLoad()
  
          let camera = GMSCameraPosition.camera(withLatitude: 15.4989, longitude: 73.8278, zoom: 6)
          mapView.camera = camera
          mapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
          mapView.isMyLocationEnabled = true
          mapView.settings.myLocationButton = true
          self.view.addSubview(self.mapView)
      }
  }
  </code></pre>
  
  <p>I went through a few other similar SO threads and all of them have the same code. In my case the UI freezes and crashes with this error. What am I doing wrong?</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>Yes, I have set the UIView's custom class as <code>GMSMapView</code></p>