Cannot convert undefined or null to object. В чем может быть проблема?

class ShowList extends Component {

  render() {
    const showList = () => Object.values(this.props.articles).map(i => {
      return (
        <li key={i.id} className="app__list__showList">
        </li>
      )
    })
    return (
      <ul className="app__list__showList">
        {showList()}
        {/* {console.log(this.props.articles)} */}
      </ul>
    );
  }
}

const mapStateToProps = state => {
  const data = state.fetchReducer;
  return {
    articles: data.data
  }
}

export default connect(mapStateToProps)(ShowList);