问Google Books API:无法读取未定义的属性“”thumbnail“”

EN

document.querySelector('.search-book').addEventListener('click', getBook);
var titleHolder = document.querySelector('.title');
var columns = document.querySelector('.is-parent');
var total = '';
const apiKey = 'AIzaSyCu0GO52L8knIMQ7P_gmazBf_7wlngXqyc';

function getBook() {
  var search = document.querySelector('#input').value;
  console.log(search);
  fetch(
    `https://www.googleapis.com/books/v1/volumes?q=${search}:keyes&key=${apiKey}`
  )
    .then(function(res) {
      return res.json();
    })
    .then(function(data) {
      //console.log(data.items);
      let items = data.items;
      for (var i = 0; i < items.length; i++) {
        // Volume info
        let item = items[i].volumeInfo;

        // Author
        let author = item.authors;

        // Image link
        var imgLink = item.imageLinks.thumbnail;

        // Title
        let title = item.title;

        // Description
        let desc = item.description;

        if (typeof desc === 'undefined') {
          desc = 'No description available';
        }

        if (typeof author === 'undefined') {
          author = 'No author';
        }

        if (!item.imageLinks.firstChild) {
          _.set(
            item,
            'item.imageLinks',
            'thumbnail:https://bulma.io/images/placeholders/128x128.png'
          );
          console.log(data);
        }

        total += `
        <div class=" card tile is-child is-3 box">
          <div class="card-image">
            <figure class="image is-4by3">
              <img src="${imgLink}" alt="Placeholder image">
            </figure>
          </div>
          <div class="card-content">
            <p class="title is-6 has-text-primary has-text-centered is-capitalized">${title}</p>
            <p class="title is-6 has-text-primary has-text-centered is-capitalized">${author}</p>
            <p class="has-text-black-ter has-text-weight-normal">${desc.slice(
              0,
              150
            ) + '...'}</p>
          </div>
        </div>
        `;

        console.log(item);
      }
      columns.innerHTML = total;
    });
}

if (!item.imageLinks.firstChild) {
              _.set(
                item,
                'item.imageLinks',
                'thumbnail:https://bulma.io/images/placeholders/128x128.png'
              );
              console.log(data);
            }