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', 'nlea78a12b8hb37opjtvfhn8k1', '216.73.216.213', '1789587975', '1789587975', '/xtshop/shop_content.php?coID=4')

[XT SQL Error]