type 'List<IdealType>' is not a subtype of type 'Widget?' of 'result'

[minjinDelable]

my test code here

  Future<void> myInfoUpdateDialog2(
    BuildContext context,
    String title,
  ) async {
    await showDialog<Widget>(
      context: context,
      builder: (BuildContext context) {
        return MultiSelectDialog(
          initialValue: controller.state.gnrProfileInfo.value.idealType,
          items: IdealType.values
              .map((IdealType e) => MultiSelectItem(e, e.value))
              .toList(),
          onConfirm: (List<dynamic> data) {
            print(data);
          },
        );
      },
    );
  }

idealType here

enum IdealType {
  P012001('P012001', '다정다감'),
  P012002('P012002', '솔직'),
  P012003('P012003', '결단력 있는'),
  P012004('P012004', '온화함'),
  P012005('P012005', '친근함'),
  P012006('P012006', '밝음'),
  P012007('P012007', '내성적'),
  P012008('P012008', '외향적'),
  P012009('P012009', '성실함'),
  P012010('P012010', '지적인'),
  P012011('P012011', '부지런한'),
  P012012('P012012', '꼼꼼한'),
  P012013('P012013', '낙천적인'),
  P012014('P012014', '밝은'),
  P012015('P012015', '품위 있는'),
  P012016('P012016', '침착한'),
  P012017('P012017', '겸손한'),
  P012018('P012018', '사려 깊은'),
  P012019('P012019', '사교적'),
  P012020('P012020', '냉정한'),
  P012021('P012021', '모험적인'),
  P012022('P012022', '가정적인'),
  P012023('P012023', '책임감 있는');

  const IdealType(this.id, this.value);

my error msg here

======== Exception caught by gesture ===============================================================
The following assertion was thrown while handling a gesture:
'package:flutter/src/widgets/navigator.dart': Failed assertion: line 4950 pos 12: '!_debugLocked': is not true.


Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
  https://github.com/flutter/flutter/issues/new?template=2_bug.md

When the exception was thrown, this was the stack: 
#2      NavigatorState.pop (package:flutter/src/widgets/navigator.dart:4950:12)
#3      Navigator.pop (package:flutter/src/widgets/navigator.dart:2433:27)
#4      MultiSelectActions.onConfirmTap (package:multi_select_flutter/util/multi_select_actions.dart:25:15)
#5      _MultiSelectDialogState.build.<anonymous closure> (package:multi_select_flutter/dialog/mult_select_dialog.dart:327:20)
#6      _InkResponseState.handleTap (package:flutter/src/material/ink_well.dart:1072:21)
#7      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:253:24)
#8      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:627:11)
#9      BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:306:5)
#10     BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:239:7)
#11     PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:615:9)
#12     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:98:12)
#13     PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:143:9)
#14     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:617:13)
#15     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:141:18)
#16     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:127:7)
#17     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:460:19)
#18     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:440:22)
#19     RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:337:11)
#20     GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:395:7)
#21     GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:357:5)
#22     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:314:7)
#23     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:295:7)
#24     _invoke1 (dart:ui/hooks.dart:167:13)
#25     PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:341:7)
#26     _dispatchPointerDataPacket (dart:ui/hooks.dart:94:31)
(elided 2 frames from class _AssertionError)
Handler: "onTap"
Recognizer: TapGestureRecognizer#302a0
  debugOwner: GestureDetector
  state: possible
  won arena
  finalPosition: Offset(277.0, 612.0)
  finalLocalPosition: Offset(21.5, 19.0)
  button: 1
  sent tap down
====================================================================================================

Ok,cancel button causes error. Why is that?