Allow "Flagging : Flag Link" view field to work on base table

I created a flag based on a simple custom content_type, created a new view with a page.

I added a view field "Flagging : Flag Link"

This error shows when I want to display the page containing this view

( ! ) Fatal error: Call to a member function getLinkTypePlugin() on null in drupal8\modules\flag\src\Plugin\views\field\FlagViewsLinkField.php on line 100

  protected function renderLink(EntityInterface $entity, ResultRow $values) {
    if (empty($entity)) {
      return '';
    }
    $flag = $this->getFlag();
    $link_type_plugin = $flag->getLinkTypePlugin(); <----- line 100
    $link = $link_type_plugin->getLink($flag, $entity);
    return $link;
  }

  public function getFlag() {
    if (isset($this->view->relationship[$this->options['relationship']])) {
      return $this->view->relationship[$this->options['relationship']]->getFlag();
    }
    return NULL;
  }

getFlag() seems to return NULL, a problem with a relationship somewhere ?