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', '8tc8ak30l3bgt7c7be64i2sv97', '216.73.216.87', '1765739844', '1765739844', '/popup_content.php?XTCsid=15cbbc13723f7bc63afaf1294f637517&coID=1')

[XT SQL Error]