public function is_admin($id_chat): ?bool
  {
    if ( $this->check() && ($chat = $this->info($id_chat)) && !$chat['blocked'] ){
      return (bool)$this->db->count('bbn_chats_users', [
        'id_chat' => $id_chat,
        'id_user' => $this->user->get_id(),
        'admin' => 1
      ]);
    }
    return null;
  }