[FIX] account: analytic account on write-off

When an analytic account is specified on a write-off move, it should be
written on the move line linked to the write-off account, as it was the
case in v8.

opw-688635

addons/account/models/account_move.py

@@ -916,8 +916,8 @@ class AccountMoveLine(models.Model):
         # Writeoff line in the account of self
         first_line_dict = vals.copy()
         first_line_dict['account_id'] = self[0].account_id.id
-        if 'analytic_account_id' in vals:
-            del vals['analytic_account_id']
+        if 'analytic_account_id' in first_line_dict:
+            del first_line_dict['analytic_account_id']
 
         # Writeoff line in specified writeoff account
         second_line_dict = vals.copy()