The short answer is that if such concerns were actually realized, the OP or the person posting a bounty (if different) could ask for Moderator intervention. Deleting the Question itself doesn't really seem to be the best approach.
If there is some unusual situation, it appears that (diamond) Moderators have a menu to remove and refund bounties, allowing for a Question to be closed and/or deleted.
In this case it does not appear that anyone has tried to "cash the bounty by giving a nonsensical answer". If this should happen, the OP would be able to flag the answer for Moderator attention. The supposed nonsense Answer could then be mod-Deleted, esp. if it seemed to be some kind of bad faith arrangement among "tricksters" to game the bounty system.