 
 public class Position: NSObject {
 
-    private var observers: NSHashTable
+    private var observers: NSHashTable?
 	
     // location types
     private let locationCenter: PositionLocationCenter

		self.activityManager.startActivityUpdatesToQueue(NSOperationQueue()) { (activity) in
			self.activityManager.stopActivityUpdates()
			
			let enumerator = self.observers.objectEnumerator()
			while let observer: PositionObserver = enumerator.nextObject() as? PositionObserver {
				self.motionActivityStatus = .Allowed
				observer.position(self, didChangeMotionAuthorizationStatus: self.motionActivityStatus)
			}

				self.activityManager.stopActivityUpdates()
				self.motionActivityStatus = .Allowed
				
				let enumerator = self.observers?.objectEnumerator()
				while let observer: PositionObserver = enumerator?.nextObject() as? PositionObserver {
					observer.position(self, didChangeMotionAuthorizationStatus: self.motionActivityStatus)
				}
			}
