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', '13jeco4ck74uhn8mu1klvpl8r1', '216.73.216.9', '1757938555', '1757938555', '/shop_content.php?XTCsid=81fba26e1f006e30d12d9ee4d58a4030&coID=8')

[XT SQL Error]