1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', '7t44ucrcjght3iurr2hba1jbe7', '216.73.216.9', '1757931246', '1757931246', '/index.php?XTCsid=02e6bd680443148f6a7ac7cc84f5c4da')

[XT SQL Error]