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', 'u3522tgh9vog8r05e4egbfm6u5', '216.73.216.9', '1757981553', '1757981553', '/shop_content.php?XTCsid=792dd2eece839333bab562194e3fb545&coID=4&language=de')

[XT SQL Error]