A Database Error Occurred

Error Number: 1048

Column 'user_id' cannot be null

INSERT INTO `paypal_transactions` (`paypal_id`, `user_id`, `checkout_url`, `approval_url`, `status`, `invoice_number`, `access_token`) VALUES ('PAYID-MYDGLOY3Y822668LH219571D', NULL, 'https://www.sandbox.paypal.com/cgi-bin/webscr?cmd=_express-checkout&token=EC-61V614892B030442H', 'https://api.sandbox.paypal.com/v1/payments/payment/PAYID-MYDGLOY3Y822668LH219571D/execute', 'created', '660665b9c18cb', 'A21AAIR_daPp8cWmGEkwDCVbH_VhBA70TG3oZnWMTNst7LfflPu-UqTauVYI6pNUXh46BNKVOHBzEAt6KIE0It96AsBTnm3zg')

Filename: models/cms/Paypal_model.php

Line Number: 33