[FIX] purchase : be able to use it with MPS

Since procurement group is passed by the optional values
in the procurement proccess it should be considered as optional

MPS do not use procurement group because they will add the
planification in an existing RFQ it will fail because purchase search
for the key 'group_id' in values

opw-1833060

addons/purchase/models/purchase.py

@@ -1016,7 +1016,7 @@ class ProcurementRule(models.Model):
 
         gpo = self.group_propagation_option
         group = (gpo == 'fixed' and self.group_id.id) or \
-                (gpo == 'propagate' and values['group_id'].id) or False
+                (gpo == 'propagate' and 'group_id' in values and values['group_id'].id) or False
 
         return {
             'partner_id': partner.id,
@@ -1041,7 +1041,7 @@ class ProcurementRule(models.Model):
         domain = super(ProcurementRule, self)._make_po_get_domain(values, partner)
         gpo = self.group_propagation_option
         group = (gpo == 'fixed' and self.group_id) or \
-                (gpo == 'propagate' and values['group_id']) or False
+                (gpo == 'propagate' and 'group_id' in values and values['group_id']) or False
 
         domain += (
             ('partner_id', '=', partner.id),