Empty administration sections for Quiz Question implementations

The iterator that finds the admin screens for each question type was outputting on admin item for type "Array". I fixed the typo in attached patch.

Now that the menu is populated with admin items for each question type, it's striking that so many of them say, "There are no settings for this question type." It might be better to only generate the item when there are actually any admin options, but I'll leave that requesting that feature to someone more bothered by it.