运行demo,什么都不操作就有几率闪退 "Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'This task has already been stopped'" <img width="852" alt="image" src="https://user-images.githubusercontent.com/17978155/123049840-93ea6f00-d432-11eb-8c7d-b8ced9463a42.png">