Queries that return empty results can fail

[dougbrn]

Bug report
@AndyTza ran into an issue recently, where he was applying a query on his nested-dask workflow. This query resulting in empty dataframes for a small subset of partitions in the dataset. The nested-pandas implementation of query has issues with this: https://github.com/lincc-frameworks/nested-pandas/blob/main/src/nested_pandas/nestedframe/core.py#L265

These issues relate to the downstream function query_flat, having this exception for an empty result: https://github.com/lincc-frameworks/nested-pandas/blob/main/src/nested_pandas/series/accessor.py#L226. The empty series seems to not work correctly in some situations, and can produce this error: TypeError: incompatible index of inserted column with frame index

Interestingly, this doesn't come up in a simple toy case:

There's a notebook on epyc (message me for the path) that can reproduce the error. So far, I've seen that simply deleting the if len(flat) == 0: section seems effective at removing the error, but we should look deeper at this and make sure we find a robust solution.

A draft PR with the rough fix is here: #128

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