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', '73egmmsjj4f98letb2e3kfhol4', '216.73.217.0', '1790113751', '1790113751', '/index.php?XTCsid=09c43bdddaf5303190cc96d38e6bc538')

[XT SQL Error]