changed how we check if contract comes from sub proposal

sponsorship_compassion/models/contract_group.py

@@ -92,10 +92,7 @@ def _should_skip_invoice_generation(self, invoicing_date, contract=None):
 
         existing_invoices = self.env["account.move"].search_count(search_filter)
 
-        previous_contract = contract.parent_id
-        is_sub_proposal = (previous_contract is not None
-                           and previous_contract.type == "S"
-                           and previous_contract.sds_state == "sub")
+        is_sub_proposal = contract.parent_id.child_id
 
         # If invoices come from sub proposal, ignore group suspension to also generate
         # already paid invoices