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', 'tunhc1q4het2jc50iqu7vk92f5', '216.73.217.152', '1791171852', '1791171852', '/shop_content.php?XTCsid=80c3e9fc87b53cb0d288d19ef4e9b63c&coID=3')

[XT SQL Error]