Bug: if the puzzle does not have a thread_ts, post_slack_message returns an error

[pil0u]

Likelyhood: low.

If for some reason the thread_ts is not set for a given puzzle, posting a solution returns an error 500 (although the solution is correctly posted).

    if @snippet.save
      post_slack_message
...
  def post_slack_message
    client = Slack::Web::Client.new
    puzzle = Puzzle.by_date(Aoc.begin_time.change(day: params[:day]))
    username = "<#{helpers.profile_url(current_user.uid)}|#{current_user.username}>"
    solution = "<#{helpers.snippet_url(day: @snippet.day, challenge: @snippet.challenge, anchor: @snippet.id)}|solution>"
    text = "#{username} submitted a new #{solution} for part #{params[:challenge]} in :#{@snippet.language}-hd:"
    client.chat_postMessage(channel: ENV.fetch("SLACK_CHANNEL", "#aoc-dev"), text:, thread_ts: puzzle.thread_ts) # <<<<< HERE
  end

⚠️ If the thread_ts is set to nil (like puzzle&.thread_ts), then the message is posted in the channel directly 😬