[UI] use safe defaults for fetching cluster logs

[FxKu]

get_teams_for_user might return an empty list which would leave team and cluster_name unbound:

2022-04-28 07:38:23,972 ERROR: Exception on /operator/clusters/default/foobar-minimal-cluster/logs [GET]
Traceback (most recent call last):
  File "/usr/lib/python3.8/site-packages/flask/app.py", line 2077, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/lib/python3.8/site-packages/flask/app.py", line 1525, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/lib/python3.8/site-packages/flask/app.py", line 1523, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/lib/python3.8/site-packages/flask/app.py", line 1509, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
  File "/operator_ui/main.py", line 207, in wrapper
    return f(*args, **kwargs)
  File "/operator_ui/main.py", line 975, in get_operator_get_logs_per_cluster
    return proxy_operator(f'/clusters/{team}/{namespace}/{cluster_name}/logs/')
UnboundLocalError: local variable 'team' referenced before assignment

[FxKu]

👍

[idanovinda]

👍

[jopadi]

👍