Gap not working in flutter version : 3.5.4

======== Exception caught by widgets library =======================================================
The following _TypeError was thrown building TabletLoginDisplay(dirty, dependencies: [_InheritedProviderScope<CMSThemeProvider?>], state: _TabletLoginDisplayState#4c301):
TypeError: Instance of 'Gap': type 'Gap' is not a subtype of type 'StatefulWidget'

The relevant error-causing widget was:
TabletLoginDisplay TabletLoginDisplay:file:///Users/yo/Projects/GitHub/gen_dashboard/lib/router/app_router.gr.dart:640:19
When the exception was thrown, this was the stack:
http://localhost:63137/dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 296:3 throw_
http://localhost:63137/dart-sdk/lib/_internal/js_shared/lib/rti.dart 1405:3 _failedAsCheck
http://localhost:63137/dart-sdk/lib/_internal/js_shared/lib/rti.dart 1383:3 _generalAsCheckImplementation
http://localhost:63137/dart-sdk/lib/_internal/js_dev_runtime/private/js_array.dart 98:39 insert]
http://localhost:63137/packages/cms/function/cms_generator.dart 434:8 tabletBody
http://localhost:63137/packages/gen_dashboard/views/template/Display/tablet/tablet_login_display.dart 28:41 build
http://localhost:63137/packages/flutter/src/widgets/framework.dart 5729:27 build
http://localhost:63137/packages/flutter/src/widgets/framework.dart 5617:15 performRebuild
http://localhost:63137/packages/flutter/src/widgets/framework.dart 5780:11 performRebuild
http://localhost:63137/packages/flutter/src/widgets/framework.dart 5333:7 rebuild
http://localhost:63137/packages/flutter/src/widgets/framework.dart 2693:14 [_tryRebuild]
http://localhost:63137/packages/flutter/src/widgets/framework.dart 2752:11 [_flushDirtyElements]
http://localhost:63137/packages/flutter/src/widgets/framework.dart 3048:17 buildScope
http://localhost:63137/packages/flutter/src/widgets/binding.dart 1162:9 drawFrame
http://localhost:63137/packages/flutter/src/rendering/binding.dart 468:5 [_handlePersistentFrameCallback]
http://localhost:63137/packages/flutter/src/scheduler/binding.dart 1397:7 [_invokeFrameCallback]
http://localhost:63137/packages/flutter/src/scheduler/binding.dart 1318:9 handleDrawFrame
http://localhost:63137/packages/flutter/src/scheduler/binding.dart 1176:5 [_handleDrawFrame]
http://localhost:63137/lib/_engine/engine/platform_dispatcher.dart 1408:5 invoke
http://localhost:63137/lib/_engine/engine/platform_dispatcher.dart 310:5 invokeOnDrawFrame
http://localhost:63137/lib/_engine/engine/initialization.dart 187:36
http://localhost:63137/dart-sdk/lib/_internal/js_dev_runtime/patch/js_allow_interop_patch.dart 188:27 _callDartFunctionFast1