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', '120d9s4h220ah3jb75bsahn947', '216.73.216.118', '1761344182', '1761344182', '/index.php?XTCsid=8c7e7b4fb3b879851ba0665526643f36')

[XT SQL Error]