Create invoice line for non-line only once

issue3292
review1043003
(transplanted from 399d66f4e5262cffe86254af3f43074f2e43418d)

purchase.py

@@ -1123,8 +1123,10 @@ class PurchaseLine(ModelSQL, ModelView):
         invoice_line.type = self.type
         invoice_line.description = self.description
         invoice_line.note = self.note
+        invoice_line.origin = self
         if self.type != 'line':
             if (self.purchase.invoice_method == 'order'
+                    and not self.invoice_lines
                     and ((all(l.quantity >= 0 for l in self.purchase.lines
                                 if l.type == 'line')
                             and invoice_type == 'in_invoice')
@@ -1179,7 +1181,6 @@ class PurchaseLine(ModelSQL, ModelView):
             if not invoice_line.account:
                 self.raise_user_error('missing_account_expense_property',
                     (invoice_line.purchase.rec_name,))
-        invoice_line.origin = self
         return [invoice_line]
 
     @classmethod