}
}
- if ($SysPrefs->check_qty_charged_vs_del_qty == true && ($_POST['qty_recd'.$n] != $_POST['prev_quantity_inv'.$n]))
+ if ($SysPrefs->check_qty_charged_vs_del_qty == true && ($_POST['qty_recd'.$n] != $_POST['prev_quantity_inv'.$n])
+ && !empty($_POST['prev_quantity_inv'.$n]))
{
if (input_num('this_quantity_inv'.$n) / ($_POST['qty_recd'.$n] - $_POST['prev_quantity_inv'.$n]) >
(1+ ($margin / 100)))