#14 Contract violation with `--list-closed`

$ prop --list-closed
string-append: contract violation
  expected: string?
  given: #<void>
  context...:
   /home/george/projects/proposal_database/proposal_database.rkt:252:0: printprop
   /home/george/projects/proposal_database/proposal_database.rkt:412:0: querysys
   body of "/home/george/projects/proposal_database/proposal_database.rkt"

(printprop) is coded to identify proposals that are either:

• submitted
• accepted
• rejected

But "closed" proposals are all those that are not submitted.