Fix annulation K-Psul

Le cas où une commande est annulée dans le temps avant CANCEL_DURATION
ne pose plus problème.

kfet/views.py

@@ -740,11 +740,12 @@ def kpsul_cancel_operations(request):
             'amount': opegroup['amount'],
             'on_acc__is_cof': opegroup['on_acc__cofprofile__is_cof'],
         })
+    canceled_by__trigramme = canceled_by and canceled_by.trigramme or None
     for ope in opes:
         websocket_data['opes'].append({
             'cancellation': True,
             'id': ope,
-            'canceled_by__trigramme': canceled_by.trigramme,
+            'canceled_by__trigramme': canceled_by,
             'canceled_at': canceled_at,
         })
     # Need refresh from db cause we used update on querysets