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', '856ij85vlglh48gqmoj8e5tc20', '216.73.217.128', '1790055102', '1790055102', '/index.php?XTCsid=a5ae7aa36aecd59295ef7c7c5e3b3701')

[XT SQL Error]