stacktrace: when node goes offline and ezo running in oracle mode

[robinagist]

Traceback (most recent call last):
File "ezo/start.py", line 47, in
main()
File "ezo/start.py", line 13, in main
app.run()
File "/Users/robin/PycharmProjects/ezo/venv/lib/python3.6/site-packages/cement/core/foundation.py", line 882, in run
return_val = self.controller._dispatch()
File "/Users/robin/PycharmProjects/ezo/venv/lib/python3.6/site-packages/cement/core/controller.py", line 477, in _dispatch
return func()
File "/Users/robin/PycharmProjects/ezo/ezo/cli/ezo_cli.py", line 147, in start
res, err = ezo.start(args.extra_args)
TypeError: 'NoneType' object is not iterable