[+] Avoid bug when select "Subscribers without an account" 

Avoid bug when select "Subscribers without an account" if $who not equal 0 or 2
[+] Avoid wrong count value when export customers and suscribers 

Db::getInstance(_PS_USE_SQL_SLAVE_)->NumRows() give last count value, but we execute 2 request.
Merge pull request #3 from cinscaen/patch-2

[-] BO : Avoid bug when select "Subscribers without an account"
Merge pull request #5 from cinscaen/patch-3

[-] BO : Avoid wrong count value when export customers and suscribers
// follow up #5
// Version updated to v2.4.4