Do not throw 500 when no votes found

[lukasotocerny]

Currently the endpoint /users/{user-id}/votes returns HTTP 500 from method getAllVotesForUser. That's not a good practice and should either return HTTP 200 [] empty array, or HTTP 404.

[DerrickGXD]

New pull request has changed the error handling from InternalServerErrorException to NotFoundException, so it should be returning HTTP 404 now.