Contacts ingest - Warning "MiddleName" too short

In ingesting a dataset (using an ISO MENDS file), we got an warning message about a couple contacts in the dataset.  Here's an example of one of them:

<gmd:pointOfContact>
<gmd:CI_ResponsibleParty>
<gmd:individualName>
<gco:CharacterString>Per Gloersen</gco:CharacterString>
</gmd:individualName>
...
</gmd:pointOfContact>

According to the spreadsheet notes (~V88), having no middle name should be legal, as it will just assume the first and last names and no middle name.  However, the ingest returns the following warning message:

After translating item to UMM-C the metadata had the following issue: /ContactPersons/1/MiddleName string "" is too short (length: 0, required minimum: 1)

Interestingly, this only happens when the Contact Name is two words long.  In the above example, if I were to remove the "Per", and just have it be one word, it ingests with no warning.  Also, of course, if I add one (or more) "middle names" it ingests with no warning, so this bug(?) seems to only be happening with the "two names" instance.