fix bug

app/helpers/export_helper.rb

@@ -92,7 +92,7 @@ module ExportHelper
             user_name = t.user&.real_name
             user_time = format_time(t.updated_at)
             user_score = t&.score
-            user_comment = t&.comment
+            user_comment = t.comment.present? ? t.comment : "--"
             comment_title = "教师:#{user_name}\n时间:#{user_time.to_s}\n分数:#{user_score.to_s}分\n评语:#{user_comment}\n\n"
             w_18 = w_18 + comment_title
           end
@@ -164,7 +164,7 @@ module ExportHelper
             user_name = t.user&.real_name
             user_time = format_time(t.updated_at)
             user_score = t&.score
-            user_comment = t&.comment
+            user_comment = t.comment.present? ? t.comment : "--"
             comment_title = "教师:#{user_name}\n时间:#{user_time.to_s}\n分数:#{user_score.to_s}分\n评语:#{user_comment}\n\n"
             # ("教师:" + user_name + "\n" + "时间:" + user_time.to_s + "\n" + "分数:" + user_score.to_s + "分" + "\n" + "评语:" + user_comment + "\n\n")
             w_18 = w_18 + comment_title