Undefined Constant - gift certificate checkout

V156c
php 7.2x
mysql 5.7

Received this warning when a customer tried to use a gift certificate. Customer could not tell me how it happened, and I have been unable to reproduce this with a specific checkout sequence.

[21-Oct-2019 19:29:13 America/New_York] Request URI: /index.php?main_page=checkout_confirmation, IP address: xxxxx
#1  ot_gv->collect_posts() called at [/usr/www/users/xxx/includes/classes/order_total.php:162]
#2  order_total->collect_posts() called at [/usr/www/users/xxx/includes/modules/pages/checkout_confirmation/header_php.php:71]
#3  require(/usr/www/users/xxx/includes/modules/pages/checkout_confirmation/header_php.php) called at [/usr/www/users/xxx/index.php:36]
--> PHP Warning: Use of undefined constant error - assumed 'error' (this will throw an Error in a future version of PHP) in /usr/www/users/xxx/includes/modules/order_total/ot_gv.php on line 236.

You can fix it by changing those final error parameters to actually be a string, by wrapping it in quotes
like this: https://github.com/zencart/zencart/commit/d233421ed4059ac774c05db3d68d638bc886de35

Thank you for the quick reply. I will make the string wrapping changes.

I also see that there's change to a line in the function apply_credit() , should I also make that change also or is that something for v157 only?

 -  global $db, $order, $messageStack;
 +  global $db, $order;