Fix _recombine_columns when either geocolumn or non-geocolumn was empty

[mroeschke]

Description

closes #1437

When GeoDataFrame._split_out_geometry_columns is called, there may be no geometry columns to split out into 2 DataFrames; therefore, once GeoDataFrame._recombine_columns, it assumed the 2 DataFrames were always non-empty. Added a check to bypass this validation if either was empty.

I ran the ZipCodes_Stops_PiP_cuSpatial notebook locally and the (non-commented) cells no longer raise an exception.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[harrism]

Looks good, just a logic simplification.

[harrism]

Thanks!

[jameslamb]

I'm interested in getting this merged to unblock CI here, so I pushed the pre-commit changes CI was complaining about (just those automatically applied by pre-commit run --all-files). Figured you wouldn't mind, @mroeschke .

[jameslamb]

/merge