【Flutterエラー対応】Error: To set up CocoaPods for ARM macOS, runError: type ‘Null’ is not a subtype of type ‘String’ in type cast

======== Exception caught by widgets library =======================================================
The following _CastError was thrown building XXXX(dirty):
type 'Null' is not a subtype of type 'String' in type cast

import 'package:flutter/material.dart';
import './question.dart';
import './answer.dart';

class Quiz extends StatelessWidget {
  final List<Map<String, Object>> questions;
  final int questionIndex;
  final Function answerQuestion;

  Quiz({
    required this.questions,
    required this.answerQuestion,
    required this.questionIndex
  });

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Question(
          questions[questionIndex]['questionText']as String
        ),
        ...(questions[questionIndex]['answers'] as List<Map<String,Object>>).map((answer) {
          return Answer(() => answerQuestion(answer['score']), answer['text']as String);
        }).toList()
      ],
    );
  }
}

import 'package:flutter/material.dart';
import './question.dart';
import './answer.dart';

class Quiz extends StatelessWidget {
  final List<Map<String, Object>> questions;
  final int questionIndex;
  final Function answerQuestion;

  Quiz({
    required this.questions,
    required this.answerQuestion,
    required this.questionIndex
  });

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Question(
          questions[questionIndex]['questionText'].toString(),
        ),
        ...(questions[questionIndex]['answers'] as List<Map<String,Object>>).map((answer) {
          return Answer(() => answerQuestion(answer['score']), answer['text'].toString());
        }).toList()
      ],
    );
  }
}