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', 'e2icn4jgq2eq0bcjf9o8oojtr0', '216.73.216.28', '1775734045', '1775734045', '/index.php?XTCsid=49fc75412bccc50f2ce0a3b1ee60899a')

[XT SQL Error]