1) Remove illogical condition.

file: catalog/checkout_payment.php

line: if (MODULE_ORDER_TOTAL_INSTALLED)

action: remove this line

2) Add missing constant.

file: catalog/includes/languages/add_ccgvdc_english.php

line: define('ERROR_NO_ACCOUNT_GV', 'You must sign in to your account to
redeem a Gift Certificate');

action: add this line

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