Bugfix: cron_task fails when last_update_success is null in DB.

ffdnispdb/utils.py

@@ -59,6 +59,8 @@ def tosystemtz(d):
     """
     Convert the UTC datetime ``d`` to the system time zone defined in the settings
     """
+    if d is None:
+        return 'None'
     return d.astimezone(pytz.timezone(current_app.config['SYSTEM_TIME_ZONE']))