HMDA Dashboard to handle null database results gracefully

[PatrickGoRaft]

There are instances in which some fields returned by the transmittal sheet query for earlier years can have null values. This results in the dashboard service throwing a NPE and returning a 500 error on the API call.

 ERROR hmda.api.http.directives.HmdaTimeDirectives$ -- Request failed, not timing it                                                  │
│ java.lang.NullPointerException: null                                                                                                                                                                │
ERROR akka.actor.ActorSystemImpl -- Error during processing of request: 'java.lang.NullPointerException (No error message supplied)' │
│ java.lang.NullPointerException: null```