Does it ever make sense to upvote an answer to a question and vote to
delete that same question?
While answers can be useful and help others even if the question is poor, in order to have an overall quality Q&A thread and useful content, the question should not be in a delete-able state. In this state, there should be no answer, and so arguably no upvotes.
If you feel the question is to be removed, then your upvote on the answer will eventually be removed anyway, based on the outcome you feel should occur. So you are essentially saying you will upvote and then also remove it later, which is pointless IMO.
From this outcome, the answerer would gain then lose rep, which is pointless, and loss of rep from deleted questions confuses some users , and uses system resources to calculate rep, send notification, and then recalc when the question is deleted.
Can the question be edited and salvaged so the decent answer can remain and help others? If so then I would do that, and so form a decent Q&A and possibly useful to others. Then of course an upvote on a decent answer is normal play.
Otherwise, my opinion, vote to delete and move on.
Personally, I dislike when people answer questions which should be removed, or are dupe etc. I don't downvote the answer (unless it's worthy), but it is frustrating that instead of answering they could have flagged/voted to delete, and answered a question which is worthwhile and helps others (ie not going to be deleted). This goes towards attaining a better all round level of quality of Q and A.
People answering delete-able questions also means OP gets their gold, which can cause OP to ask another poor/lazy question because they got an answer last time. Your upvote can add to showing that we accept such things because there is an answer and people are upvoting it.
Bad posts should be handled as such, including the answers.