Redundant empty prefix checked needlessly by validate

[matentzn]

When validating the file below:

sssom validate mp_hp_owt_impc.sssom.tsv

I get:

check_all_prefixes_in_curie_map
    raise ValidationError(
jsonschema.exceptions.ValidationError: The prefixes in [''] are missing from 'curie_map'.

This can be fixed by adding another orcid into the reviewer column. Something is wrong with the way the prefixes are extracted from the table?

# creator_id: orcid:0000-0002-2232-0967
# curie_map:
#   HP: http://purl.obolibrary.org/obo/HP_
#   MP: http://purl.obolibrary.org/obo/MP_
#   owl: http://www.w3.org/2002/07/owl#
#   rdf: http://www.w3.org/1999/02/22-rdf-syntax-ns#
#   rdfs: http://www.w3.org/2000/01/rdf-schema#
#   skos: http://www.w3.org/2004/02/skos/core#
#   sssom: https://w3id.org/sssom/
#   orcid: https://orcid.org/
#   obo: http://purl.obolibrary.org/obo/
#   semapv: https://w3id.org/semapv/
# license: https://creativecommons.org/publicdomain/zero/1.0/
# mapping_provider: https://www.mousephenotype.org
# mapping_set_description: 'The IMPC Mouse Morphology Mappings: Organ Weight Test'
# mapping_set_id: mp_hp_owt_impc
subject_id	subject_label	predicate_id	object_id	object_label	mapping_justification	reviewer_id
MP:0001259	abnormal body weight	skos:exactMatch	HP:0004323	Abnormality of body weight	semapv:LexicalMatching	orcid:0000-0002-7356-1779
MP:0002707	abnormal kidney weight	skos:closeMatch	HP:0000077	Abnormality of the kidney	semapv:LogicalReasoning