NULL is not subtype of type 'Map<dynamic, dynamic> in type cast (Lesson #30)

[Kweldop]

======== Exception caught by widgets library =======================================================
The following _CastError was thrown building Home(dirty, dependencies: [_ModalScopeStatus], state: _HomeState#30fff):
type 'Null' is not a subtype of type 'Map<dynamic, dynamic>' in type cast

The relevant error-causing widget was:
Home Home:file:///D:/world-clock/worldclock/lib/main.dart:12:29
When the exception was thrown, this was the stack:
#0 _HomeState.build (package:worldclock/pages/home.dart:18:59)
#1 StatefulElement.build (package:flutter/src/widgets/framework.dart:4992:27)
#2 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4878:15)
#3 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#4 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#5 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4859:5)
#6 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:5041:11)
#7 ComponentElement.mount (package:flutter/src/widgets/framework.dart:4853:5)
... Normal element mounting (275 frames)
#282 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3863:16)
#283 MultiChildRenderObjectElement.inflateWidget (package:flutter/src/widgets/framework.dart:6435:36)
#284 MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6447:32)
... Normal element mounting (416 frames)
#700 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3863:16)
#701 Element.updateChild (package:flutter/src/widgets/framework.dart:3592:18)
#702 RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:1195:16)
#703 RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:1164:5)
#704 RenderObjectToWidgetAdapter.attachToRenderTree. (package:flutter/src/widgets/binding.dart:1111:18)
#705 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2605:19)
#706 RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:1110:13)
#707 WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:945:7)
#708 WidgetsBinding.scheduleAttachRootWidget. (package:flutter/src/widgets/binding.dart:925:7)
(elided 4 frames from class _RawReceivePortImpl, class _Timer, and dart:async-patch)

======== Exception caught by widgets library =======================================================
The following _CastError was thrown building Home(dirty, dependencies: [_ModalScopeStatus], state: _HomeState#30fff):
type 'Null' is not a subtype of type 'Map<dynamic, dynamic>' in type cast

The relevant error-causing widget was:
Home Home:file:///D:/world-clock/worldclock/lib/main.dart:12:29
When the exception was thrown, this was the stack:
#0 _HomeState.build (package:worldclock/pages/home.dart:18:59)
#1 StatefulElement.build (package:flutter/src/widgets/framework.dart:4992:27)
#2 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4878:15)
#3 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#4 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#5 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#6 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#7 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#8 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#9 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#10 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#11 StatelessElement.update (package:flutter/src/widgets/framework.dart:4956:5)
#12 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#13 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#14 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#15 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#16 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#17 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#18 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#19 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#20 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#21 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#22 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#23 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#24 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#25 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#26 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#27 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#28 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#29 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#30 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#31 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#32 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#33 StatelessElement.update (package:flutter/src/widgets/framework.dart:4956:5)
#34 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#35 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#36 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#37 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#38 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#39 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#40 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#41 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#42 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#43 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#44 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#45 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#46 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#47 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#48 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#49 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#50 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#51 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#52 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#53 StatelessElement.update (package:flutter/src/widgets/framework.dart:4956:5)
#54 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#55 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#56 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#57 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#58 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#59 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#60 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#61 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#62 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#63 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#64 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#65 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#66 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#67 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#68 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#69 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#70 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#71 StatelessElement.update (package:flutter/src/widgets/framework.dart:4956:5)
#72 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#73 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#74 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#75 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#76 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#77 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#78 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#79 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#80 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#81 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#82 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#83 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#84 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#85 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#86 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#87 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#88 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#89 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#90 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#91 StatelessElement.update (package:flutter/src/widgets/framework.dart:4956:5)
#92 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#93 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#94 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#95 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#96 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#97 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#98 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#99 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#100 StatelessElement.update (package:flutter/src/widgets/framework.dart:4956:5)
#101 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#102 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#103 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#104 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#105 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#106 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#107 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#108 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#109 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#110 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#111 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#112 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#113 ProxyElement.update (package:flutter/src/widgets/framework.dart:5228:5)
#114 _InheritedNotifierElement.update (package:flutter/src/widgets/inherited_notifier.dart:107:11)
#115 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#116 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#117 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#118 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#119 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#120 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#121 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#122 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#123 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#124 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#125 ProxyElement.update (package:flutter/src/widgets/framework.dart:5228:5)
#126 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#127 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#128 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#129 ProxyElement.update (package:flutter/src/widgets/framework.dart:5228:5)
#130 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#131 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#132 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#133 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#134 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#135 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#136 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#137 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#138 StatelessElement.update (package:flutter/src/widgets/framework.dart:4956:5)
#139 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#140 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#141 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#142 StatelessElement.update (package:flutter/src/widgets/framework.dart:4956:5)
#143 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#144 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6307:14)
#145 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#146 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#147 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#148 ProxyElement.update (package:flutter/src/widgets/framework.dart:5228:5)
#149 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#150 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#151 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#152 ProxyElement.update (package:flutter/src/widgets/framework.dart:5228:5)
#153 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#154 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#155 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#156 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#157 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#158 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#159 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#160 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#161 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#162 StatefulElement.update (package:flutter/src/widgets/framework.dart:5082:5)
#163 Element.updateChild (package:flutter/src/widgets/framework.dart:3570:15)
#164 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4904:16)
#165 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5050:11)
#166 Element.rebuild (package:flutter/src/widgets/framework.dart:4604:5)
#167 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2667:19)
#168 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:882:21)
#169 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:378:5)
#170 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1175:15)
#171 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1104:9)
#172 SchedulerBinding.scheduleWarmUpFrame. (package:flutter/src/scheduler/binding.dart:881:7)
(elided 4 frames from class _RawReceivePortImpl, class _Timer, and dart:async-patch)

[Bioust]

try this
data = ModalRoute.of(context)!.settings.arguments as Map <dynamic, dynamic>;