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', 'kfeoddkm5a5stlkv7p60fr5204', '18.97.9.169', '1771363387', '1771363387', '/xtshop/index.php?cat=c13_.html')

[XT SQL Error]