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', '354d0483df0d5406adc0ff2951ceca49', '35.173.48.224', '1566096319', '1566096319', '/index.php/cat/c1_Natur--Wasserabziehsteine.html/XTCsid/354d0483df0d5406adc0ff2951ceca49')

[XT SQL Error]