Column 'author' doesn't belong to any of the selected models (2)

Hello All,

I get this error message "Column 'author' doesn't belong to any of the selected models (2)" when select data from database using querybuilder as follow

     $builder = $this->modelsManager->createBuilder()
         ->from('Webapp\Frontend\Models\Blog')
         ->where('author = :author:',array("author" => $auth[id]))
         ->orderBy('Webapp\Frontend\Models\Blog.id');

     // Create a Model paginator, show 10 rows by page starting from $currentPage
     $paginator = new \Phalcon\Paginator\Adapter\QueryBuilder(
         array(
             "builder" => $builder,
             "limit"=> 10,
             "page" => $currentPage
         )
     );
     $page = $paginator->getPaginate();
     $this->view->setVar("page", $page);

I use the same method when select data from other table and they working fine but not work with my last create table.

class Blog extends \Phalcon\Mvc\Model
{

/**
 *
 * @var integer
 */
public $id;

/**
 *
 * @var integer
 */
public $author;

/**
 *
 * @var integer
 */
public $category;

/**
 *
 * @var string
 */
public $title;

/**
 *
 * @var string
 */
public $slug;

/**
 *
 * @var string
 */
public $intro;

/**
 *
 * @var string
 */
public $content;

public function initialize()
{

}

}

MySQL Column

1. id int(11)
2. author int(11)
3. category int(11)
4. title varchar(255)
5. slug varchar(255)
6. intro varchar(255)
7. content longtext

What I do wrong on this query builder?

another question - what is meaning of (2) in "Column 'author' doesn't belong to any of the selected models (2)"?

Thank you for any help.