thematic-accuracy-land-cover: Address `UndefinedMetricWarning`

[matthiasschaub]

When running tests the following warning is issued:

  /home/matthias/.cache/pypoetry/virtualenvs/ohsome-quality-api-KPaXoOaM-py3.11/lib64/python3.11/site-packages/sklearn/metrics/_c
lassification.py:1565: UndefinedMetricWarning:
  
  Precision is ill-defined and being set to 0.0 in labels with no predicted samples. Use `zero_division` parameter to control thi
s behavior.