Pedometro ritorna "nil"

        if(CMPedometer.isStepCountingAvailable()){
            let fromDate = NSDate(timeIntervalSinceNow: -3600)
            pedometer.queryPedometerData(from: fromDate as Date, to: Date()) { (data : CMPedometerData!, error) -> Void in
                print(data)
               DispatchQueue.main.async { () -> Void in
                    if(error == nil){
                        self.dateLabel.text = "\(data.numberOfSteps)"
                    }
                }
              
            }
    }