diff --git a/app/controllers/subjects_controller.rb b/app/controllers/subjects_controller.rb
index 92976e05a..efc117d6a 100644
--- a/app/controllers/subjects_controller.rb
+++ b/app/controllers/subjects_controller.rb
@@ -242,7 +242,8 @@ class SubjectsController < ApplicationController
     ## 云上实验室过滤
     @courses = @courses.where(id: current_laboratory.all_courses)
 
-    @none_shixun_ids = @subject.shixuns.joins(:shixun_schools).where("school_id != #{current_user.user_extension.try(:school_id).to_i}").where(use_scope: 1).pluck(:id)
+    @all_shixun_ids = @subject.shixuns.where(use_scope: 0).pluck(:id) +
+      @subject.shixuns.joins(:shixun_schools).where("school_id = #{current_user.user_extension.try(:school_id).to_i} and use_scope = 1").pluck(:id)
   end
 
   def send_to_course
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 40e6cb365..7e5926bab 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -137,7 +137,7 @@ module ApplicationHelper
 
   # 用户图像url，如果不存在的话，source为匿名用户，即默认使用匿名用户图像
   def url_to_avatar(source)
-    if File.exist?(disk_filename(source.class, source.id))
+    if File.exist?(disk_filename(source&.class, source&.id))
       ctime = File.ctime(disk_filename(source.class, source.id)).to_i
       if source.class.to_s == 'User'
         File.join(relative_path, ["#{source.class}", "#{source.id}"]) + "?t=#{ctime}"
diff --git a/app/views/homework_commons/works_list.json.jbuilder b/app/views/homework_commons/works_list.json.jbuilder
index cd2f17cf5..9fb2d6971 100644
--- a/app/views/homework_commons/works_list.json.jbuilder
+++ b/app/views/homework_commons/works_list.json.jbuilder
@@ -171,7 +171,7 @@ elsif @homework.homework_type == "group" || @homework.homework_type == "normal"
 
     json.user_login @is_evaluation ?  "--" : work.user.try(:login)
     json.user_name @is_evaluation ? "匿名" : work.user.try(:real_name)
-    json.user_img url_to_avatar(@is_evaluation ? "0" : work.user)
+    json.user_img @is_evaluation ? "--" : url_to_avatar(work.user)
 
   end
 end
diff --git a/app/views/subjects/choose_course.json.jbuilder b/app/views/subjects/choose_course.json.jbuilder
index 2e03c5287..8dae4e3e4 100644
--- a/app/views/subjects/choose_course.json.jbuilder
+++ b/app/views/subjects/choose_course.json.jbuilder
@@ -7,7 +7,7 @@ end
 json.stages @subject.stages.includes(shixuns: [user: :user_extension]) do |stage|
   index = 1
   json.shixuns stage.shixuns do |shixun|
-    if shixun.status == 2 && !shixun.is_jupyter && !@none_shixun_ids.include?(shixun.id)
+    if shixun.status == 2 && !shixun.is_jupyter && @all_shixun_ids.include?(shixun.id)
       json.shixun_id shixun.id
       json.id shixun.id
       json.identifier shixun.identifier