Start object cache if needed

src/wp-includes/l10n.php

@@ -2050,6 +2050,7 @@ static function ( $a, $b ) use ( $codes, $prios ) {
  * Only works if either the object cache or the database are already available.
  */
  if ( wp_using_ext_object_cache() || wp_installing() ) {
+ wp_start_object_cache();
  $translations = wp_cache_get( 'available_translations', 'site-transient' );
  } elseif ( isset( $wpdb ) ) {
  $translations = get_site_option( '_site_transient_available_translations' );