tests: invalid value encountered in divide

[pjonsson]

Here's an excerpt of the test logs:

2025-07-25 20:36:40 [info     ] Task commencing                task=AlchemistTask(dataset=Dataset <id=7e96b76a-6b02-4427-9a1d-3c9104f2db96 product=ga_ls7e_ard_3 location=s3://dea-public-data/baseline/ga_ls7e_ard_3/102/071/2020/09/09/ga_ls7e_ard_3-1-0_102071_2020-09-09_final.stac-item.json>, settings=AlchemistSettings(specification=Specification(measurements=['nbart_blue', 'nbart_green', 'nbart_red', 'nbart_nir', 'nbart_swir_1', 'nbart_swir_2', 'oa_fmask'], transform='wofs.virtualproduct.WOfSClassifier', transform_url='https://github.com/GeoscienceAustralia/wofs/', product=None, products=['ga_ls5t_ard_3', 'ga_ls7e_ard_3', 'ga_ls8c_ard_3'], measurement_renames={'oa_fmask': 'fmask'}, transform_args={'dsm_path': 'https://dea-public-data.s3-ap-southeast-2.amazonaws.com/projects/elevation/ga_srtm_dem1sv1_0/dem1sv1_0.tif'}, transform_args_per_product=None, resampling=None, override_product_family='ard', basis='nbart_green', aws_unsigned=True), output=OutputSettings(location='/tmp/alchemist', write_data_settings={'overview_resampling': <Resampling.mode: 6>}, nodata=1, preview_image=None, preview_image_singleband={'measurement': 'water', 'lookup_table': {0: [150, 150, 110], 1: [0, 0, 0], 16: [119, 104, 87], 32: [89, 88, 86], 64: [216, 215, 214], 80: [242, 220, 180], 128: [79, 129, 189], 160: [51, 82, 119], 192: [186, 211, 242]}}, metadata={'product_family': 'wo', 'producer': 'ga.gov.au', 'dataset_version': '1.6.0', 'collection_number': '3', 'naming_conventions': 'dea_c3'}, properties={'dea:dataset_maturity': 'interim'}, reference_source_dataset=True, write_stac=True, inherit_geometry=True, explorer_url='https://explorer.dev.dea.ga.gov.au/'), processing=ProcessingSettings(dask_chunks={'x': -1, 'y': 4096}, dask_client={})))
/usr/local/lib/python3.10/dist-packages/wofs/__init__.py:1: UserWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refrain from using this package or pin to Setuptools<81.
  from pkg_resources import get_distribution, DistributionNotFound
2025-07-25 20:36:45 [info     ] Data loaded                    task=UUID('7e96b76a-6b02-4427-9a1d-3c9104f2db96')
/usr/local/lib/python3.10/dist-packages/wofs/classifier.py:81: RuntimeWarning: divide by zero encountered in divide
  c = (a - b) / (a + b)
/usr/local/lib/python3.10/dist-packages/wofs/terrain.py:114: RuntimeWarning: overflow encountered in multiply
  norm_len = numpy.sqrt((xgrad * xgrad) + (ygrad * ygrad) + 1.0)
/usr/local/lib/python3.10/dist-packages/wofs/terrain.py:117: FutureWarning: The return type of `Dataset.dims` will be changed to return a set of dimension names in future, in order to be more consistent with `DataArray.dims`. To access a mapping from dimension names to lengths, please use `Dataset.sizes`.
  x, y = tile.dims.keys()
/usr/local/lib/python3.10/dist-packages/wofs/terrain.py:120: RuntimeWarning: invalid value encountered in divide

The last line prints invalid value encountered in divide, which I'm guessing is a division by NaN.