Fatal error MapKit Swift 2

Hello I was trying to load a map for my application of IOs with a certain location and the appropriate zoom was following a tutorial but in my house there is an error, I attached the image of the error that appears in addition to the map code. in this case I am using Xcode 7 and Swift 2.

  

fatal error: unexpectedly found nil while unwrapping an Optional value

import UIKit
import MapKit

class ViewController: UIViewController {


    @IBOutlet weak var mapView: MKMapView!

    override func viewDidLoad() {
        super.viewDidLoad()
        maptal()

    }

    func maptal()
    {
        let tallat:CLLocationDegrees = 27.175015
        let tallon:CLLocationDegrees = 78.042139

        let tajcordinate = CLLocationCoordinate2D(latitude: tallat, longitude: tallon )

        let latdelta:CLLocationDegrees = 0.01
        let longdelta:CLLocationDegrees = 0.01

        let tajspan = MKCoordinateSpan(latitudeDelta: latdelta, longitudeDelta: longdelta)

        let tajregion = MKCoordinateRegion(center: tajcordinate, span: tajspan)

        mapView.setRegion(tajregion, animated: true)

        let tajanotation = MKPointAnnotation()
        tajanotation.title = "taj mahal"
        tajanotation.subtitle = "holita"
        tajanotation.coordinate = tajcordinate

        mapView.addAnnotation(tajanotation)

    }

}