I have Zen cart 1.5.6b with PHP 7.3 and getting the below warning

[23-Jun-2019 13:53:33 Australia/Melbourne] Request URI: /xxxx/orders.php?cID=20525&page=1&oID=20993&action=edit, IP address: 49.197.64.63
#1 dirbankaus->update_status() called at [/home/x/public_htmlxxx/includes/modules/payment/dirbankaus.php:41]
#2 dirbankaus->dirbankaus() called at [/home/xxxx/public_html/gdadmin/orders.php:420]
--> PHP Warning: Illegal string offset 'id' in /home/xxxxx/public_html/includes/modules/payment/dirbankaus.php on line 50.


line 50 dirbankaus.php is below:
$check = $db->Execute("select zone_id from " . TABLE_ZONES_TO_GEO_ZONES . " where geo_zone_id = '" . MODULE_PAYMENT_DIRBANKAUS_ZONE . "' and zone_country_id = '" . $order->delivery['country']['id'] . "' order by zone_id");

From my reading I don't think this error can be fixed in line 50. It might need to be fixed in line 41 below?:
if (is_object($order)) $this->update_status();