fix rake

lib/tasks/course_board_message_count.rake

@@ -5,13 +5,15 @@ namespace :course_board do
       logger("Current transfer board id: #{board.id} ~")
 
       root_subquery = board.messages.where(parent_id: nil).reorder(nil).pluck(:id)
-      next if root_subquery.blank?
-      children_subquery = Message.where(parent_id: root_subquery).reorder(nil).pluck(:id)
-      next if children_subquery.blank?
-      second_children_subquery = Message.where(parent_id: children_subquery).reorder(nil).pluck(:id)
+      if root_subquery.present?
+        children_subquery = Message.where(parent_id: root_subquery).reorder(nil).pluck(:id)
+        if children_subquery.present?
+          second_children_subquery = Message.where(parent_id: children_subquery).reorder(nil).pluck(:id)
 
-      ids = children_subquery.concat(second_children_subquery).uniq
-      Message.where(id: ids).update_all(board_id: board.id)
+          ids = children_subquery.concat(second_children_subquery).uniq
+          Message.where(id: ids).update_all(board_id: board.id)
+        end
+      end
 
       Board.reset_counters(board.id, :messages)
       logger("transfer success ~")