Handle empty parquet files when batching and no destinations are within distance of origins

[ethan-moss]

Description of the Feature to be Added

When batching, if there are no destination centroids within distance of the origin then it writes empty parquet files.

(OPTIONAL) Suggested Implementations

After filtering to required origins and destinations in od_matrix() (and before _calculate_transport_network is called), the following snippet could be used to skip this case:

if len(dest_gdf) == 0:
    continue

Additional context