Prior to this fix we could exit early if tags was `[]` as `tags && (tags & post.topic.tags.map(&:name)).empty?` would have returned true. This commit ensures it's not the case anymore and adds a test for it.
Co-Authored-By: Martin Brennan <mjrbrennan@gmail.com>
Prior to this fix the query in stalled_topic_finder would assume that tags/categories would be nil or an array of ids. However it can be an empty array, in this case the query will not return results.
