react js中的单选按钮验证。未选择任何内容时，无法获取错误消息

import React, { Component } from 'react';

class RadioButtonGroup extends Component {
  constructor(props) {
    super(props);
    this.state = {
      selectedValue: null,
      error: ''
    };
  }

  handleRadioChange = (event) => {
    this.setState({
      selectedValue: event.target.value,
      error: ''
    });
  }

  handleSubmit = (event) => {
    event.preventDefault();
    if (this.state.selectedValue === null) {
      this.setState({
        error: '请选择一个选项'
      });
    } else {
      // 执行提交操作
    }
  }

  render() {
    return (
      <form onSubmit={this.handleSubmit}>
        <div>
          <label>
            <input
              type="radio"
              value="option1"
              checked={this.state.selectedValue === 'option1'}
              onChange={this.handleRadioChange}
            />
            选项1
          </label>
        </div>
        <div>
          <label>
            <input
              type="radio"
              value="option2"
              checked={this.state.selectedValue === 'option2'}
              onChange={this.handleRadioChange}
            />
            选项2
          </label>
        </div>
        <div>
          <label>
            <input
              type="radio"
              value="option3"
              checked={this.state.selectedValue === 'option3'}
              onChange={this.handleRadioChange}
            />
            选项3
          </label>
        </div>
        {this.state.error && <div>{this.state.error}</div>}
        <button type="submit">提交</button>
      </form>
    );
  }
}

export default RadioButtonGroup;