[2.0.x] [BUG] fixing bug and other enchantments

[KorsaR-ZN]

fixing bug (prev PR #10166):

$builder = $model->getModelsManager()->createBuilder()
->columns($columns)
   ->addFrom('CartItems', 's')
   ->where('s.cart_id="6086"')
   ->groupBy('s.product_id');

echo $readConnection->getDialect()->select($q->getQuery()->parse());

Result:

SELECT ``, ``, ``, ``, ``, ``, ``, ``, ``, ``, ``, ``, ``, ``, ``, `` FROM `cart_items` AS `s` WHERE `s`.`cart_id` = '6086' GROUP BY `s`.`product_id`

And also fix for #10160, #10135

[KorsaR-ZN]

@andresgutierrez Build failed after commit 5e33a16
see, build passed - https://travis-ci.org/KorsaR-ZN/phalcon-core/builds/60859518

[andresgutierrez]

Thanks