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', '2d9s0ul3tnm9g6n1t9iqf7e8q7', '216.73.216.82', '1752525869', '1752525869', '/index.php?cat=c4_Beer-Mugs.html&XTCsid=3547ee950f9337e348e5e07def1466f0')

[XT SQL Error]