fix bug

app/controllers/zips_controller.rb

@@ -49,12 +49,12 @@ class ZipsController < ApplicationController
           @course = @exercise.course
 
           default_ex_users = @exercise.all_exercise_users(current_user.id).exercise_user_committed
-          @ex_users =  default_ex_users.limit 1   #仅导出已提交的，截止后则是全部为提交的。
+          @ex_users =  default_ex_users   #仅导出已提交的，截止后则是全部为提交的。
           #可以分班选择
           if group_id.present?
             exercise_students = @course.students.where(course_group_id: group_id)  # 试卷所分班的全部人数
             user_ids = exercise_students.pluck(:user_id).reject(&:blank?).uniq
-            @ex_users = @ex_users.where(user_id: user_ids).limit 1
+            @ex_users = @ex_users.where(user_id: user_ids)
           end
 
           default_ex_users_size = @ex_users.size