[FIX] calendar: day of month is expected filled in code
[FIX] calendar: day of month is expected filled in code

Before this commit there was an error when we chose a monthly recurrence
with "Day of Month" of type "Day of" because the code expect them to be
set. In any case they are required field so if they are not field we
should just ignore it.

opw-702852

dfang/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,dfang/odoo,ygol/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,dfang/odoo,hip-odoo/odoo