Empty columns are not returned in json view of pbdb_occurrences

[javigzz]

Hello,
Some time ago we received an issue for the R package (ropensci/paleobioDB#18) regarding the response to the json requests. By comparing with the txt or csv version, the json requests for pbdb_occurrences do not include the empty columns.
In the issue linked you may see it with
https://paleobiodb.org/data1.1/occs/list.txt?base_name=Dicellograptus&show=abund&limit=all and
https://paleobiodb.org/data1.1/occs/list.json?limit=all&base_name=Dicellograptus&show=abund&vocab=pbdb
where the json lacks the "reid_no","superceded","abund_value","abund_unit" contrary to the txt.

Is this a know / desired behavior? Although is not too problematic, it could potentially cause some issue if lets say a second request expects (or not expects) some given columns which do not come come (or do come) with a first request. Would be desirable to get even the empty columns for consistency.

Thanks!
Javier