flutter 集成报错 null

android 小米8 使用 flutter ^0.8.0-nullsafety.0 这个版本进入应用报错 flutter版本 2.0.4

报错信息如下：

Dart Unhandled Exception: Bad state: implemented internally, stack trace: #0 Nested.build (package:nested/nested.dart:81:5)
E/flutter ( 9977): #1 _DoKitWrapper.build (package:dokit/ui/dokit_app.dart:52:52)
E/flutter ( 9977): #2 StatelessElement.build (package:flutter/src/widgets/framework.dart:4569:28)
E/flutter ( 9977): #3 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4495:15)
E/flutter ( 9977): #4 Element.rebuild (package:flutter/src/widgets/framework.dart:4189:5)
E/flutter ( 9977): #5 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2694:33)
E/flutter ( 9977): #6 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:873:21)
E/flutter ( 9977): #7 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:319:5

oSuchMethodError: The getter 'headers' was called on null.
Receiver: null
Tried calling: headers
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5)
#1 DoKitHttpClientRequest.headers (package:dokit/engine/dokit_http.dart:237:37)
#2 _WebSocketImpl.connect. (dart:_http/websocket_impl.dart:1036:15)
#3 _rootRunUnary (dart:async/zone.dart:1362:47)
#4 _CustomZone.runUnary (dart:async/zone.dart:1265:19)
#5 _FutureListener.handleValue (dart:async/future_impl.dart:152:18)
#6 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:704:45)
#7 Future._propagateToListeners (dart:async/future_impl.dart:733:32)
#8 Future._completeWithValue (dart:async/future_impl.dart:539:5)
#9 _completeOnAsyncReturn (dart:async-patch/async_patch.dart:254:13)
#10 DoKitHttpClient.monitor (package:dokit/engine/dokit_http.dart)