Splitting of sparse features (including points) fails with 500 error

[spwoodcock]

Describe the bug

Some very sparse data extracts passed into fmtm-splitter, for example:

Fail with an error like:

psycopg2.errors.InternalError_: K (49) must be smaller than the number of rows in the group (48)

To Reproduce

Try and split a very sparse data extract in FMTM, for example using the heathcare category.

Expected behavior

• The buildings should be split by the desired number of buildings per task, although I'm sure that's easier said than done!

Additional context

• The data extract actually contains 105 features, many of which are point rather than polygon, so perhaps this is also the issue.

[spwoodcock]