When I use a singleton to call a type object, the program crashes.

The specific error is as follows, which can be solved:

 

08:57:46. 508 XYZ [707: 1403] *** assertion failure in-[uikeyboardtaskqueue failed],/sourcecache/uikit_sim/UIKit-2935.137/keyboard/uikeyboardtaskqueue. M: 368

08:57:46. 509 XYZ [707: 1403] *** terminating app due to uncaught exception 'nsinternalinconsistencyexception', reason: '-[uikeyboardtaskqueue waituntilalltasksarefinished] may only be called from the main thread.'

*** First throw call Stack:

(

0 corefoundation 0x0266e1e4 _ predictionpreprocess + 180

1 libobjc. A. dylib 0x023ed8e5 objc_exception_throw + 44

2 corefoundation 0x0266e048 + [nsexception raise: Format: arguments:] + 136

3 Foundation 0x01fcd4de-[nsassertionhandler handlefailureinmethod: object: file: linenumber: Description:] + 116

4 uikit 0x01800166-[uikeyboardtaskqueue waituntilalltasksarefinished] + 167

5 uikit 0x0128ff11-[uikeyboardimpl setdelegate: Force:] + 442

6 uikit 0x0128fd52-[uikeyboardimpl setdelegate:] + 60

7 uikit 0x01556dc5-[uiperipheralhost (uikitinternal) _ reloadinputviewsforresponder:] + 956

8 uikit 0x01560a0e-[uiperipheralhost (uikitinternal) _ preserveinputviewswithid: animated:] + 550

9 uikit 0x011d7940-[uiviewcontroller presentviewcontroller: withtransition: Completion:] + 3317

10 uikit 0x10f9078f-[uiviewcontrolleraccessibility (safecategory) presentviewcontroller: withtransition: Completion:] + 71

11 uikit 0x011d8aef-[uiviewcontroller presentviewcontroller: animated: Completion:] + 130

12 XYZ 0x0007e613 _ 33-[loginviewcontroller userlogin:] _ block_invoke + 483

13 Foundation 0x02109ac5 _ 67 + [nsurlconnection sendasynchronousrequest: queue: completionhandler:] _ block_invoke_2 + 151

14 Foundation 0x02068d65-[nsblockoperation main] + 88

15 Foundation 0x020c1c79-[_ nsoperationinternal _ start:] + 671

16 Foundation 0x0203e9c8-[nsoperation start] + 83

17 Foundation 0x020c3f44 _ nsoqschedule_f + 62

18 libdispatch. dylib 0x030854d0 _ dispatch_client_callout + 14

19 libdispatch. dylib 0x03071fe0 _ dispatch_async_redirect_invoke + 202

20 libdispatch. dylib 0x030854d0 _ dispatch_client_callout + 14

21 libdispatch. dylib 0x03073eb7 _ dispatch_root_queue_drain + 291

22 libdispatch. dylib 0x03074127 _ dispatch_worker_thread2 + 39

23 libsystem_pthread.dylib 0x033b4dab _ pthread_wqthread + 336

24 libsystem_pthread.dylib 0x033b8cce start_wqthread + 30

)

Libc ++ Abi. dylib: terminating with uncaught exception of Type nsexception