Memory leak with UIAlertController in Swift

I am presenting a simple UIViewController using this simple code

@IBAction func addNewFeed(sender: UIBarButtonItem)
{

    var alertView: UIAlertController? = UIAlertController(title: NSLocalizedString("New Feed", comment: "Titolo popup creazione feed"),
        message: NSLocalizedString("Insert the Title and the Link for the new Feed.", comment: "Messaggio creazione nuovo feed"),
        preferredStyle: UIAlertControllerStyle.Alert)


    alertView!.addAction(UIAlertAction(title: NSLocalizedString("Cancel", comment: "Annulla popup creazione nuovo feed"),
        style: UIAlertActionStyle.Cancel,
        handler: nil))

    presentViewController(alertView!, animated: true, completion: nil)

}

      

        
        
        
      

    

When I click a button on my interface, I call this IBAction and the UIAlertController appears. But when I click the Cancel button to close the controller, the Leak Tool has detected a leak, as you can see in this image:

I tried to put a closure like this in the handler parameter:

alertView!.addAction(UIAlertAction(title: NSLocalizedString("Cancel", comment: "Annulla popup creazione nuovo feed"),
        style: UIAlertActionStyle.Cancel,
        handler: {[weak self] action in self!.dismissViewControllerAnimated(true, completion: nil)
        alertView = nil
        }))

      

        
        
        
      

    

but there is always a leak.