How to reproduce the bug ======================== 1.Open the register page of an event 2.Do not pick any ticket 3.Click Register => an traceback is raised Technical ========= '?.length > 0' statement was checking the length of the array instead of the values of the array. This issue comes after this https://github.com/odoo/odoo/pull/120437 After this commit: ================== Now the traceback will not raise. Task-3329432 closes odoo/odoo#126352 X-original-commit: 1c47606cf1cd56c4d0980c7419c508e37c90f58f Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>