[FIX] ir_model: stop crashing _prepare_update
[FIX] ir_model: stop crashing _prepare_update

If the field being checked in _prepare_update hasn't been loaded yet we
should skip it to avoid a KeyError.

OPW-1871180
OPW-1872236
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo