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', 'he6ljkikcf8l9e1ldqvkconkv2', '216.73.216.180', '1766927408', '1766927408', '/index.php?XTCsid=1f7d4bf9ab18ba26ae6d57d5fd1ea044')

[XT SQL Error]