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', '2flt9od92cdkan2fvfifgpefe2', '216.73.216.40', '1773538424', '1773538424', '/product_info.php?XTCsid=adc8c520bddaa9e02a40df1e2a90f128&info=p15_25-balloons.html')

[XT SQL Error]