footer.php

    <footer class="site-footer" role="contentinfo">

        <?php if ($page->template() == "project" || $page->template() == "article"):
            $featured = $pages->find('projecten')->children()->shuffle()->limit(4); ?>

            <div class="random-content container">
                <a href="/projecten"><h3 class="random-content-title">Meer projecten</h3></a>
                <ul class="collection">
                  <?php foreach($featured as $project): ?>
                  <li class="collection-item project">
                    <a href="<?php echo $project->url() ?>">
                        <img src="<?= $project->images()->sortBy('sort', 'asc')->first()->thumb(array('width' => 300))->url() ?>" alt="Thumbnail for the project <?= $project->title()->html() ?>" class="project-thumbnail" />
                    </a>
                    <h4><?php echo $project->title() ?></h4>
                  </li>
                  <?php endforeach ?>
                </ul>
            </div>

        <?php endif ?>
      
      …
      
</footer>

kirby error

Error thrown with message "Call to a member function thumb() on null"

Stacktrace:
#11 Error in /var/www/html/site/snippets/footer.php:12
#10 require in /var/www/html/kirby/vendor/getkirby/toolkit/lib/tpl.php:22
#9 Tpl:load in /var/www/html/kirby/kirby/component/snippet.php:38
#8 Kirby\Component\Snippet:render in /var/www/html/kirby/helpers.php:12
#7 snippet in /var/www/html/site/templates/project.php:26
#6 require in /var/www/html/kirby/vendor/getkirby/toolkit/lib/tpl.php:22
#5 Tpl:load in /var/www/html/kirby/kirby/component/template.php:103
#4 Kirby\Component\Template:render in /var/www/html/kirby/kirby.php:635
#3 Kirby:template in /var/www/html/kirby/kirby.php:623
#2 Kirby:render in /var/www/html/kirby/kirby/component/response.php:29
#1 Kirby\Component\Response:make in /var/www/html/kirby/kirby.php:705
#0 Kirby:launch in /var/www/html/index.php:16