flight_data_to_arrow_batch does not support RecordBatches with no columns

[SuperTails]

Describe the bug

Attempting to use flight_data_to_arrow_batch on flight data that does not have any columns returns an InvalidArgumentError("must either specify a row count or at least one column").

To reproduce

Call flight_data_to_arrow_batch on a FlightData and Schema that does not have any columns.

Expected behavior

Calling flight_data_to_arrow_batch should use the row information in the RecordBatch header and return a valid record batch instead of returning an error.

Additional context

Support for RecordBatches with no columns but with a row count was already added in #1552. flight_data_to_arrow_batch already has the row count information provided as an argument. It gets read there in message.header_as_record_batch(), but then the subsequent reader::read_record_batch call seems to discard that info.

[tustvold]

Thanks for the report, I'll bash this one out before the next release unless someone else picks it up 😀