[FIX] web: hang when saving then discarding

When editing a record, if it cannot be saved (b.e. due to required
fields) and the user clicks on save, then on discard

Before this fix, the window did nothing (seems like it is unresponsive)

After this fix, the user is able to discard the form.

task-id: 1937142

closes odoo/odoo#30871