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', 'ptem4maci4kqnbk6iocvb1e653', '216.73.216.141', '1751427731', '1751427731', '/index.php?cat=c4_Beer-Mugs.html&XTCsid=81fba26e1f006e30d12d9ee4d58a4030')

[XT SQL Error]