- Remove two redundant go_back_to_new calls in build_results, since
@poll.questions.find already raises RecordNotFound if a question
does not exist.
- Drop the fallback flash translation error_create, which is no longer
used since commit 592fdffe4e and only remained as a default in
go_back_to_new.
- Move check_officer_assignment from Officing::BaseController to
Officing::ResultsController, its only place of use.