[13.0][FIX] contract: Impossible to create invoices from contract lines as section

contract/models/contract_line.py

@@ -543,6 +543,9 @@ class ContractLine(models.Model):
         name = self._insert_markers(dates[0], dates[1])
         invoice_line_vals.update(
             {
+                "account_id": invoice_line_vals["account_id"]
+                if "account_id" in invoice_line_vals and not self.display_type
+                else False,
                 "quantity": self._get_quantity_to_invoice(*dates),
                 "product_uom_id": self.uom_id.id,
                 "discount": self.discount,
@@ -1060,4 +1063,4 @@ class ContractLine(models.Model):
         self, period_first_date, period_last_date, invoice_date
     ):
         self.ensure_one()
-        return self.quantity
+        return self.quantity if not self.display_type else 0.0

contract/tests/test_contract.py

@@ -135,6 +135,15 @@ class TestContractBase(common.SavepointCase):
                 "recurring_rule_type": "monthly",
                 "date_start": "2018-02-15",
                 "contract_line_ids": [
+                    (
+                        0,
+                        0,
+                        {
+                            "product_id": False,
+                            "name": "Header for Services",
+                            "display_type": "line_section",
+                        },
+                    ),
                     (
                         0,
                         0,