fix typo

banking/admin.py

@@ -80,7 +80,7 @@ class PendingPaymentUpdateFormSet(BaseInlineFormSet):
 
     def save_existing(self, form, instance, commit=True):
         old = PaymentUpdate.objects.get(pk=instance.pk)
-        if not obj.validated:
+        if not instance.validated:
             notify_payment_update(self.request, instance, old)
         return super().save_existing(form, instance, commit)