Do not change account nor journal of invoice no more draft

Closes #12146
(grafted from 73697963ab5783d8dfe531d0997ac58e48d19994)

--HG--
branch : 6.0

modules/account_invoice/invoice.py

@@ -436,8 +436,11 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin):
         if self.company:
             return self.company.party.id
 
-    @fields.depends('party', 'type', 'accounting_date', 'invoice_date')
+    @fields.depends(
+        'state', 'account', 'party', 'type', 'accounting_date', 'invoice_date')
     def on_change_with_account(self):
+        if self.state != 'draft':
+            return self.account
         account = None
         if self.party:
             with Transaction().set_context(