Hi,
Change the line:
$query='SELECT COUNT(name) FROM '.hikashop_table('users',false).' as u LEFT JOIN '.hikashop_table('user').' as a ON u.id=a.user_cms_id '.$filters;
to:
$query='SELECT COUNT(name) FROM '.hikashop_table('users',false).' as u LEFT JOIN '.hikashop_table('user').' as a ON u.id=a.user_cms_id LEFT JOIN '.hikashop_table('order').' AS o ON a.user_id=o.order_user_id '.$filters;
in the file /administrator/components/com_hikashop/classes/widget.php and it should fix the problem.
We'll include the change for the next version of HikaShop.