When a Term is edited, the Issued date stays but loses its date type

[wickr]

Describe the bug
When a Term is created, Issued date is set with the correct type. "2019-07-22"^^<http://www.w3.org/2001/XMLSchema#date> But when it's edited again and that is reviewed, it loses the date type. "2019-07-22" The original Issued date is still saved correctly.

To Reproduce
Steps to reproduce the behavior:

1. Create new Term
2. Review new Term
3. Visit newly created Term page, click on N-Triples
4. Check Issued date has type: <http://opaquenamespace.org/ns/test/issued_test> <http://purl.org/dc/terms/issued> "2019-07-22"^^<http://www.w3.org/2001/XMLSchema#date> .
5. Edit same Term.
6. Review edit.
7. Visit Term page, check N-Triples again, this time it's: <http://opaquenamespace.org/ns/test/issued_test> <http://purl.org/dc/terms/issued> "2019-07-22" .

Expected behavior
Issued date's type should always be retained through edits.