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', '68b8f4bd840a0069decdadff4051bf8b', '216.73.216.42', '1763383856', '1763383856', '/shop/product_info.php?info=p9_.html')

[XT SQL Error]