- fetchWithQuestionsAndCandidates / fetchWithQuestions used INNER JOINs on
questions/answers, so quizzes with no questions threw NoResultException (500)
when opening the overview tab. Switched to LEFT JOINs.
- answerMapping bare \assert() replaced with a proper flash + redirect when
the quiz has no questions, instead of crashing with AssertionError.
- Three raw 'success' flash strings in QuizController replaced with FlashType::Success.
- Added Dutch translation for "This quiz has no questions yet".
- Two new tests: empty-quiz overview loads (200), answer-mapping redirects with flash.
