AddURL processor throws cache metatada error in REST resource

Trying to get field values with

/** @var \Drupal\search_api\Item\Item $item */
$item->getFields();
// or
$item->getField('url');

throws error

The controller result claims to be providing relevant cache metadata, but leaked metadata was detected. Please ensure you are not rendering content too early. Returned object class: Drupal\rest\ResourceResponse.

This happens when Index has URL value for item.

How to reproduce bug:

• Create search index and add URI (search_api_url) field and re-index content.
• Create custom REST resource for GET drush generate rest-resource or drupal gprr.
• Write custom Search API request for index where URI field exist. Not matter what you choose for parse mode and other stuff. Try to call $item->getFields() or $item->getField('url')->getValues().
• Enable REST and make request to it. And you will see the exception.

My simple code to copy-paste for test:

<?php

namespace Drupal\MUMODULE\Plugin\rest\resource;

use Drupal\rest\Plugin\ResourceBase;
use Drupal\rest\ResourceResponse;
use Drupal\search_api\Entity\Index;
use Psr\Log\LoggerInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Represents how to throw bug in REST resource.
 *
 * @RestResource (
 *   id = "search_api_bug_example",
 *   label = @Translation("Search API bug example"),
 *   uri_paths = {
 *     "canonical" = "/api/search-api-bug",
 *   }
 * )
 */
class SearchApiUriBug extends ResourceBase {

  /**
   * {@inheritdoc}
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, array $serializer_formats, LoggerInterface $logger) {
    parent::__construct($configuration, $plugin_id, $plugin_definition, $serializer_formats, $logger);
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->getParameter('serializer.formats'),
      $container->get('logger.factory')->get('rest')
    );
  }

  /**
   * Responds to GET requests.
   */
  public function get() {
    $index = Index::load('global_index');
    /** @var \Drupal\search_api\Plugin\views\query\SearchApiQuery $query */
    $query = $index->query();
    /** @var \Drupal\search_api\ParseMode\ParseModePluginManager $parse_mode */
    $parse_mode = \Drupal::service('plugin.manager.search_api.parse_mode')
      ->createInstance('direct');
    $query->setParseMode($parse_mode);
    $query->keys('TEST');
    $query->setFulltextFields();
    $query->range(0, 5);
    $search_result = $query->execute();

    if ($search_result->getResultCount()) {
      /** @var \Drupal\search_api\Item\Item $item */
      foreach ($search_result as $item) {
        $item->getFields();
      }
    }
    return new ResourceResponse('You will not see it ;)');
  }

}