bug: algorithm crash `AttributeError: 'NoneType' object has no attribute 'empty'`

[garobrik]

Traceback #10, occurred 1 times. Example pedon: 12652, lat: 31.8872223, lon: -101.9194412
  Traceback (most recent call last):
    File "/home/roux/projects/terraso/soil-id-algorithm/soil_id/tests/us/generate_bulk_test_results.py", line 53, in <module>
      lat = pedon["y"].values[0]
                        ~~~~~^^^
    File "/home/roux/projects/terraso/soil-id-algorithm/soil_id/us_soil.py", line 95, in list_soils
      mucompdata_pd = extract_mucompdata_STATSGO(lon, lat)
    File "/home/roux/projects/terraso/soil-id-algorithm/soil_id/utils.py", line 1402, in extract_mucompdata_STATSGO
      if not mucompdata_out.empty:
             ^^^^^^^^^^^^^^^^^^^^
  AttributeError: 'NoneType' object has no attribute 'empty'

[garobrik]

after some further thought, i think this may be due to poor handling of transient errors in the STATSGO API. so related to #108, and relatively low priority from a user perspective since the backend will already retry in this case, so we wouldn't want the behavior to change for the user. and it just usually occurs quite infrequently. but we would like to communicate this better to the user, as described in #108, so i think we should leave it open as a reminder.