On corrige la détection des users anonymes

src/agenda_culturel/models.py

@@ -935,7 +935,7 @@ class Event(models.Model):
         self.no_modification_date_changed = True
 
     def set_processing_user(self, user):
-        if user.is_anonymous:
+        if user is None or user.is_anonymous:
             self.processing_user = None
         else:
             self.processing_user = user