Validation endpoint fails with 400 error code when validating a MARC Bib with empty 245 field

Steps to reproduce:

1. Send a request to validation endpoint with field `{ tag: ‘245’, content: '' }

2. Observe response

Expected result: collection of issues for the MARC record

Actual result: request fails with 400 error code and error message {"message":"Invalid converter: ","type":"-1","code":"BAD_REQUEST"}