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', 'jhs9e5b88qbo8e8g91h43kjdi4', '216.73.216.9', '1758198796', '1758198796', '/index.php?XTCsid=dc3b0270c322cee1fc32256197e30efa')

[XT SQL Error]