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', 'r478h4skevgj831ckvo96cvlf4', '216.73.216.138', '1782856742', '1782856742', '/index.php?XTCsid=aef2dc8c336966edd5aaf8c610d27e5d')

[XT SQL Error]