Issue #3266704 by MegaChriz: Fixed PHP 8.1: do not pass null to Html::escape()...

namespace Drupal\feeds\Controller;

use Drupal\Component\Datetime\TimeInterface;

use Drupal\Component\Utility\Html;

use Drupal\Component\Utility\Unicode;

use Drupal\Core\Controller\ControllerBase;

use Drupal\Core\Datetime\DateFormatterInterface;

use Drupal\Core\Entity\EntityInterface;

use Drupal\Core\Entity\Exception\UndefinedLinkTemplateException;

use Drupal\feeds\FeedInterface;

use Drupal\feeds\Plugin\Type\Processor\EntityProcessorInterface;

      // Imported ago.

      $row[] = $this->t('@time ago', ['@time' => $ago]);

      // Item GUID.

      $row[] = [

        'data' => Html::escape(Unicode::truncate($entity->get('feeds_item')->guid, 30, FALSE, TRUE)),

        'data' => $this->getPropertyFromFeedsItem($entity, 'guid'),

        'title' => $entity->get('feeds_item')->guid,

      ];

      // Item URL.

      $row[] = [

        'data' => Html::escape(Unicode::truncate($entity->get('feeds_item')->url, 30, FALSE, TRUE)),

        'data' => $this->getPropertyFromFeedsItem($entity, 'url'),

        'title' => $entity->get('feeds_item')->url,

      ];

    return $build;

  }

  /**

   * Returns a property of the feeds item.

   *

   * @param \Drupal\Core\Entity\EntityInterface $entity

   *   The imported entity that is being listed.

   * @param string $property

   *   The property to get from the feeds item.

   *

   * @return string|null|mixed

   *   If the value on the feed is a string, it will be returned truncated to 30

   *   characters. In case it is not a string, but still a scalar value, the

   *   value will be returned as is. Null is returned when it is not a scalar

   *   value.

   */

  protected function getPropertyFromFeedsItem(EntityInterface $entity, string $property) {

    $value = $entity->get('feeds_item')->{$property};

    if (!is_scalar($value)) {

      return NULL;

    }

    if (!is_string($value)) {

      return $value;

    }

    return Unicode::truncate($value, 30, FALSE, TRUE);

  }

}