private function loadVersion()
    {
        try
        {
            $this->dao = $this->db->getDAO(DBVersion::class);
            $this->db_version = 
                $this->dao->get(
                    QB::where(["module" => $this->module]), 
                    QB::order(['migration_date' => 'DESC'])
                ) 
                ?: new NullVersion;
        }
        catch (TableNotExistsException $e)
        {
            if ($this->module !== "wedeto.db")
            {
                throw new NoMigrationTableException(); 
            }
            $this->db_version = new NullVersion;
        }
    }