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', '9jcpds6cu2a5ta4modqm7g9381', '54.162.109.90', '1495804384', '1495804384', '/shop_content.php?coID=98&ecardID=869')

[XT SQL Error]