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', 'mnh2dtld4uc2kiog2t2i58s4u4', '216.73.217.108', '1788956077', '1788956077', '/products_new.php?XTCsid=274ec9b60c94b159bd8f2b261ed48387')

[XT SQL Error]