作品列表为空时缺评列表报错

app/controllers/student_work_controller.rb

@@ -245,6 +245,9 @@ class StudentWorkController < ApplicationController
   def student_work_absence_penalty
     render_403 unless User.current.allowed_to?(:as_teacher,@course)
     order = params[:order] || "desc"
+    if @homework.student_works.empty?
+      @stundet_works = []
+    else
       work_ids = "(" + @homework.student_works.map(&:id).join(",") + ")"
       @stundet_works = StudentWork.find_by_sql("SELECT *,(all_count - has_count) AS absence FROM(
       SELECT * ,
@@ -254,6 +257,7 @@ class StudentWorkController < ApplicationController
       WHERE homework_common_id = #{@homework.id}
       ) AS table_1
       ORDER BY absence #{order}")
+    end
     @order = order == "desc" ? "asc" : "desc"
     respond_to do |format|
       format.html