Issue #3272830 by acbramley: Update index throws exception if index doesn't exist

   * {@inheritdoc}

   */

  public function updateIndex(IndexInterface $index): void {

    if ($this->indexExists($index)) {

      $index->clear();

      $this->updateSettings($index);

      $this->updateFieldMapping($index);

    }

    else {

      $this->addIndex($index);

    }

  }

  /**

   * Updates the field mappings for an index.