[FIX] - log message for invoice creation only when there is an invoice

contract/models/contract.py

@@ -453,10 +453,12 @@ class ContractContract(models.Model):
         even if their next invoicing date is in the future.
         """
         invoice = self._recurring_create_invoice()
+        if invoice:
             self.message_post(
                 body=_(
                     'Contract manually invoiced: '
-                '<a href="#" data-oe-model="%s" data-oe-id="%s">Invoice</a>'
+                    '<a href="#" data-oe-model="%s" data-oe-id="%s">Invoice'
+                    '</a>'
                 )
                 % (invoice._name, invoice.id)
             )