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', '9qu8ajncuij3fufct8irhbu386', '216.73.216.50', '1781168834', '1781168834', '/product_info.php?XTCsid=3ebb0a65f1d97984fe7ad858bccc1d2f&info=p15_25-balloons.html')

[XT SQL Error]