评论关卡位置为空时，默认第一关

'

app/services/shixuns_service.rb

@@ -128,7 +128,8 @@ class ShixunsService
         manager = current_user.manager_of_shixun?(dis, current_user)
         game_url =
             if manager
-              challenge_id = dis.challenges.where(position: d.position).pluck(:id).first
+              position = d.position.nil? ? 1 : d.position
+              challenge_id = dis.challenges.where(position: position).pluck(:id).first
               game_identifier = Game.where(user_id: current_user,
                                            challenge_id: challenge_id).pluck(:identifier).first
               "/tasks/#{game_identifier}"