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', '11351b6b32f21efe6aba37f4b49e02ef', '216.73.216.132', '1759445149', '1759445149', '/shop/index.php?cat=c16_.html')

[XT SQL Error]