Crash in ZoneStatusRetrieveAjaxView views from getlist()

[mikkonie]

In staging we observed a crash in ZoneStatusRetrieveAjaxView, dump below in comments.

Looks like we're trying to use getlist() on a dict, which is generally not a good idea :)

How to Reproduce: Navigate to ProjectZonesView in a project with no landing zones available.

Spec

• Fix the landingzones JQuery to not call for the Ajax view if no zones are in the UI
• Fix the Ajax view to gracefully handle not receiving any zones in its call
  • Just in case it does get called
  • Just return an empty status_dict and a 200
• Add an ajax view to test for the view handling an "empty" request

[mikkonie]

Dump (UUID is from an imaginary project on our staging server so no secret info here):

Internal Server Error: /landingzones/ajax/status/retrieve/874ca631-05c1-4232-8491-9b9d0fbfd2bc

AttributeError at /landingzones/ajax/status/retrieve/874ca631-05c1-4232-8491-9b9d0fbfd2bc
'dict' object has no attribute 'getlist'

(...)

Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 509, in dispatch
    response = self.handle_exception(exc)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 469, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
    raise exc
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "/usr/src/app/landingzones/views_ajax.py", line 25, in post
    zone_uuids = request.data.getlist('zone_uuids[]')

[mikkonie]

Fixed by @gromdimon.