ZC 1.5.7C usinga slightly modified Responsive Classic template
PHP Version: 7.3.32 (Zend: 3.3.32)
MySQL 5.7.30
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I started receiving this error a few days ago when I won a charge back dispute through Paypal for an order that was paid by CC manually and is not associated with an order through ZenCart. Any ideas on how to stop the IPN callback or a pointer to a configuration change to keep errors like this from occuring would be greatly appreciated.

Code:
[28-Nov-2021 09:47:05 America/New_York] Request URI: /ipn_main_handler.php, IP address: 173.0.81.65
#1 trigger_error() called at [/includes/classes/db/mysql/query_factory.php:170]
#2 queryFactory->show_error() called at [/includes/classes/db/mysql/query_factory.php:142]
#3 queryFactory->set_error() called at [/includes/classes/db/mysql/query_factory.php:269]
#4 queryFactory->Execute() called at [/includes/functions/database.php:44]
#5 zen_db_perform() called at [/ipn_main_handler.php:419]
--> PHP Fatal error: 1366:Incorrect decimal value: '' for column 'mc_fee' at row 1 :: INSERT INTO paypal (order_id, txn_type, module_name, module_mode, reason_code, payment_type, payment_status, pending_reason, invoice, mc_currency, first_name, last_name, payer_business_name, address_name, address_street, address_city, address_state, address_zip, address_country, address_status, payer_email, payer_id, payer_status, payment_date, business, receiver_email, receiver_id, txn_id, parent_txn_id, num_cart_items, mc_gross, mc_fee, settle_amount, settle_currency, exchange_rate, notify_version, verify_sign, date_added, memo) VALUES ('20744', 'parent', 'paypal (ipn-handler)', 'IPN', 'chargeback_reimbursement', '', 'Completed', '', '3165-1628894647-[Mystore]', 'USD', '', '', '', '', '', '', '', '', '', '', '[email protected]', 'Z6PFML62KA2D4', 'verified', '2021-11-26 09:09:56', '', '', '', '49L67964SW698244C', '8C060304EJ230962J', '1', '225.85', '', '0', '', '1', '3.9', 'AtUbgugC4KybUOS9Xzrs4wqyfk7uAUAqom0B9gFibfjxN5omDN9aT-O-', now(), '{Record generated by IPN}') ==> (as called by) /includes/functions/database.php on line 44 <== in /includes/classes/db/mysql/query_factory.php on line 170.