Unable to capture city, and country values from Facebook iOS SDK in Swift

I am currently using the Facebook iOS SDK to capture email, first, and last name successfully in my app. However, for some reason, I am having difficulty capturing the location information such as city, and country for the user.

Here is my relevant code:

override func viewDidLoad() {
        
        super.viewDidLoad()
        fbLoginButton.delegate = self
        fbLoginButton.readPermissions = ["email", "public_profile", "user_location"]
}

extension RegisterViewController: FBSDKLoginButtonDelegate {
    
    func loginButtonDidLogOut(_ loginButton: FBSDKLoginButton!) {
        print("Did log out of facebook")
    }
    
    func loginButton(_ loginButton: FBSDKLoginButton!, didCompleteWith result: FBSDKLoginManagerLoginResult!, error: Error!) {
        if error != nil {
            print(error)
            return
        }
        
        print("Successfully logged in with facebook...")
        FBSDKGraphRequest(graphPath: "/me", parameters: ["fields": "id, name, first_name, last_name, email, location{location}"]).start { (connection, result, err) in
            
            if err != nil {
                print("Failed to start graph request:", err)
                return
            }
            
            print(result)
            
            let fbDetails = result as! NSDictionary
            let location : NSDictionary! = fbDetails.value(forKey: "location") as! NSDictionary //code crashes here
            let locationContents : NSDictionary! = location.value(forKey: "location") as! NSDictionary
            let city: String! = locationContents.value(forKey: "city") as? String
            let state: String! = locationContents.value(forKey: "state") as? String
            let country: String! = locationContents.value(forKey: "country") as? String
        
            print(fbDetails)
            print("city:", city)
            print("state:", state)
            print("country:", country)
            
            
        }
    }
}

When I run the code, in my console, I see the output for email, first_name, last_name, id, name, but nothing for location, and my app crashes with:

fatal error: unexpectedly found nil while unwrapping an Optional value 

when it reaches the line:

let location : NSDictionary! = fbDetails.value(forKey: "location") as! NSDictionary

What am I doing wrong?

You need to add 'user_location' to your read_permission.

fbLoginButton.readPermissions = ["email", "public_profile", "user_location"]

Remember to verify this permission in your fb application.(user_location is not default allowed permissions)