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', '8b5d3gbgc94bfe7abo04dfm7e5', '216.73.217.114', '1781098086', '1781098086', '/shop_content.php?XTCsid=7a53dc57544f424e178883984417ebd9&coID=7')

[XT SQL Error]