Small and easy improvement for "Products Per Page" and "Products Per Row"

Hi, 
Each category has the options "Products Per Page" and "Products Per Row". In order to follow the global options the user has to set these fields to 0. But this is not so obvious. It would be very helpful to allow empty value to follow global options. But if an empty value is set, the following error appears: 
Incorrect integer value: '' for column `eshop`.`j4_eshop_categories`.`products_per_page` at row 1
It could be good to allow the empty value (best for usability) or transform the empty value to zero.



Thanks
 

Hello,

I will fix this small issue on the next version of EShop.

Sincerely, Giang