EventKit Not working

in MacOS Mojave beta 4 EventKit is Not working I tried to access reminders from the default Calendar and event though access is granted it still says "thread 4: Fatal error: Unexpectedly found nil while unwrapping an Optional value" not sure why?

eventStore = EKEventStore()
    
        
        eventStore.requestAccess(to: .reminder) { (granted, error) in
            if granted{
                allReminders = [EKReminder]()
                
                 let cal = eventStore.defaultCalendarForNewReminders()
                let predicate = eventStore.predicateForIncompleteReminders(withDueDateStarting: nil, ending: nil, calendars: [cal!])
               
                eventStore.fetchReminders(matching: predicate, completion: { (reminders: [EKReminder]?) -> Void in
                    
                    allReminders = reminders!
                    

                })