Oops, no luck:
[2] pry(main)> t = Topic.find(1946)
=> #<Topic id: 1946, title: "Are we being excessive in not allowing re-saving o...", last_posted_at: nil, created_at: "2015-05-22 00:50:51", updated_at: "2015-05-22 00:50:51", views: 24, posts_count: 0, user_id: 81, last_post_user_id: 81, reply_count: 0, featured_user1_id: nil, featured_user2_id: nil, featured_user3_id: nil, avg_time: nil, deleted_at: nil, highest_post_number: 0, image_url: nil, off_topic_count: 0, like_count: 0, incoming_link_count: 0, bookmark_count: 0, category_id: 8, visible: true, moderator_posts_count: 0, closed: false, archived: false, bumped_at: "2015-05-22 00:50:51", has_summary: false, vote_count: 0, archetype: "regular", featured_user4_id: nil, notify_moderators_count: 0, spam_count: 0, illegal_count: 0, inappropriate_count: 0, pinned_at: nil, score: nil, percent_rank: 0.0, notify_user_count: 0, subtype: nil, slug: "are-we-being-excessive-in-not-allowing-re-saving-o...", auto_close_at: nil, auto_close_user_id: nil, auto_close_started_at: nil, deleted_by_id: nil, participant_count: 1, word_count: nil, excerpt: nil, pinned_globally: false, auto_close_based_on_last_post: false, auto_close_hours: nil>
[3] pry(main)> PostDestroyer.new(Discourse.system_user, t.posts.first).destroy
NoMethodError: undefined method `trash!' for nil:NilClass
from /var/www/discourse/lib/post_destroyer.rb:73:in `block in perform_delete'