Getting a type error of undefined for person.thumbnail causes Promise .catch() to trigger + Solution

// Generate the markup for each profile
function generateHTML(data) {
  data.map( person => {
    const section = document.createElement('section');
    peopleList.appendChild(section);
    section.innerHTML = ''; // Initialize as blank

    // Check if request returns a 'standard' page from Wiki
    if (person.type === 'standard') {

      // Some people do not have a thumbnail, and so person.thumbnail is undefined
      // This causes the .catch() on the Promise object to trigger!
      if (person.thumbnail) {
        section.innerHTML += `<img src=${person.thumbnail.source}>`;
      } 

      section.innerHTML += `
        <h2>${person.title}</h2>
        <p>${person.description}</p>
        <p>${person.extract}</p>
      `;
    } else {
      section.innerHTML += `
        <img src="img/profile.jpg" alt="ocean clouds seen from space">
        <h2>${person.title}</h2>
        <p>Results unavailable for ${person.title}</p>
        ${person.extract_html}
      `;
    }
  });
}