minor bug fixes to handle case where a nomen actually does have a parent_no, which will be increasingly common as these get filled in
minor bug fixes to handle case where a nomen actually does have a parent_no, which will be increasingly common as these get filled in

paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new,paleobiodb/pbdb-new