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, http_referer) values ('', 'Guest', '0352s5nktpi6im704agc4dmpd7', '172.17.0.19', '1455171484', '1455171484', '/shop/product_info.php?info=p1186_15-12-2012-DARK-TRANQUILLITY.html', '')

[XT SQL Error]