Run Example broken

**Describe the bug**
Just clone getx and run example broked:
```
======== Exception caught by widgets library =======================================================
The following assertion was thrown building Builder:
Navigator.onGenerateRoute returned null when requested to build route "/".

The onGenerateRoute callback must never return null, unless an onUnknownRoute callback is provided as well.
The Navigator was: NavigatorState#94170(lifecycle state: initialized)
lifecycle state: initialized
The relevant error-causing widget was:
Directionality Directionality:file:///Users/taotao/Documents/repo/getx/lib/get_navigation/src/root/get_material_app.dart:217:12
When the exception was thrown, this was the stack:
#0 NavigatorState._routeNamed. (package:flutter/src/widgets/navigator.dart:4190:11)
#1 NavigatorState._routeNamed (package:flutter/src/widgets/navigator.dart:4200:8)
#2 Navigator.defaultGenerateInitialRoutes (package:flutter/src/widgets/navigator.dart:2856:28)
#3 NavigatorState.restoreState (package:flutter/src/widgets/navigator.dart:3454:41)
#4 RestorationMixin._doRestore (package:flutter/src/widgets/restoration.dart:984:5)
#5 RestorationMixin.didChangeDependencies (package:flutter/src/widgets/restoration.dart:970:7)
#6 NavigatorState.didChangeDependencies (package:flutter/src/widgets/navigator.dart:3500:11)
#7 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4826:11)
#8 ComponentElement.mount (package:flutter/src/widgets/framework.dart:4638:5)
#9 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3673:14)
#10 Element.updateChild (package:flutter/src/widgets/framework.dart:3422:20)
#11 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#12 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#13 StatelessElement.update (package:flutter/src/widgets/framework.dart:4746:5)
#14 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#15 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#16 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#17 ProxyElement.update (package:flutter/src/widgets/framework.dart:5020:5)
#18 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#19 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#20 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#21 ProxyElement.update (package:flutter/src/widgets/framework.dart:5020:5)
#22 Element.updateChild (package:flutter/src/widgets/framework.dart:3412:15)
#23 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4690:16)
#24 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4840:11)
#25 Element.rebuild (package:flutter/src/widgets/framework.dart:4355:5)
#26 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2620:33)
#27 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:882:21)
#28 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:319:5)
#29 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1143:15)
#30 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1080:9)
#31 SchedulerBinding.scheduleWarmUpFrame. (package:flutter/src/scheduler/binding.dart:863:7)
(elided 11 frames from class _RawReceivePortImpl, class _Timer, dart:async, and dart:async-patch)
====================================================================================================

```

**Flutter Env:**
[✓] Flutter (Channel stable, 2.5.3, on macOS 11.6 20G165 darwin-x64, locale zh-Hans-CN)
• Flutter version 2.5.3 at /Users/taotao/Documents/flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 18116933e7 (5 week ago), 2021-10-15 10:46:35 -0700
• Engine revision d3ea636dc5
• Dart version 2.14.4