Our current policy is that if there is a question with an upvoted answer, the asker should not edit that question to clarify his intention if it invalidates the answer. In my experience, when that happens, someone usually rolls back the edit.
But what should we do when there is an answer to a question that "answers" the question by pointing out how the question never really gets started. This might be the case for the specific example that the OP is asking about; nonetheless, the question might still be an interesting question regardless of the situation. Can the OP edit the question in that case to invalidate a positively-received answer, or should the OP ask a new question?
The example that triggered this question is this revision which was made after this answer. I was about to roll back the revision to the question, but since the answer circumvents the question to begin with, I wanted to ask the Meta community first.