Error when no ssids are returned

[nniehoff]

Environment

• Python version: 3.7
• Nautobot version: 1.3
• ipfabric version: latest

When no wireless ssids are returned from the API the following stack trace appears in the worker:

[2022-05-18 12:23:51,172: ERROR/ForkPoolWorker-2] Task nautobot_chatops.utils.celery_worker_task[b567414b-a44c-4bd5-8b0f-014717d03220] raised unexpected: AttributeError("'NoneType' object has no attribute 'lower'")
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/celery/app/trace.py", line 451, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/celery/app/trace.py", line 734, in __protected_call__
    return self.run(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/nautobot_chatops/utils.py", line 40, in celery_worker_task
    return function(
  File "/usr/local/lib/python3.10/site-packages/nautobot_chatops_ipfabric/worker.py", line 66, in ipfabric
    return handle_subcommands("ipfabric", subcommand, **kwargs)
  File "<decorator-gen-1>", line 2, in handle_subcommands
  File "/usr/local/lib/python3.10/site-packages/prometheus_client/context_managers.py", line 81, in wrapped
    return func(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/nautobot_chatops/workers/__init__.py", line 298, in handle_subcommands
    result = registry[command]["subcommands"][subcommand]["worker"](dispatcher, *params)
  File "/usr/local/lib/python3.10/site-packages/nautobot_chatops/workers/__init__.py", line 187, in wrapper
    return func(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/nautobot_chatops_ipfabric/worker.py", line 692, in wireless
    ssids = [(ssidi["wlanSsid"].lower()) for ssidi in ipfabric_api.get_wireless_ssids(snapshot_id)]
  File "/usr/local/lib/python3.10/site-packages/nautobot_chatops_ipfabric/worker.py", line 692, in <listcomp>
    ssids = [(ssidi["wlanSsid"].lower()) for ssidi in ipfabric_api.get_wireless_ssids(snapshot_id)]
AttributeError: 'NoneType' object has no attribute 'lower'