Free/busy blocks with empty time slots breaks `calendars.availability` request

[kwayebopp]

Describe the bug When passing the result of calling the free/busy endpoint to calendars.availability, I recieve a Nylas::InvalidRequest error with the message free_busy.0.time_slots: Missing data for required field.

To Reproduce

    # nylas here is just the value returned from Nylas::API.new
    # start_time and end_time should be on a day where the user has no calendar events/busy blocks.

    nylas.calendars.availability(
      **{ duration_minutes: duration_minutes,
          interval_minutes: interval_minutes || duration_minutes,
          start_time: start_time,
          end_time: end_time,
          emails: emails,
          free_busy:  nylas.free_busy(
                                emails: emails,
                                start_time: start_time.to_i,
                                end_time: end_time.to_i
                             ),
          open_hours: open_hours,
          calendars: [
            ...
          ] })
    )

Expected behavior I expected to receive a list of available times for the user. It isn't quite clear to me why this should break on a day that has no busy blocks. I was able to achieve this by using nylas.free_busy(...).reject { |block| block.time_slots.blank? }.

SDK Version: 5.13.0

Additional context Using Ruby 3.0.2

[mrashed-dev]

Thanks for opening this issue, I'll take a look as to why this is breaking on blanks and have a solution soon.