Merge remote-tracking branch 'origin/dev_aliyun' into dev_aliyun

app/controllers/exercise_questions_controller.rb

@@ -501,9 +501,11 @@ class ExerciseQuestionsController < ApplicationController
           if ex_answers.present?   #学生有回答时 取学生的答题得分，否则0分
             answer_choice_array = []
             ex_answers.each do |a|
-              answer_choice_array.push(a.exercise_choice.choice_position)  #学生答案的位置
+              if a.try(:exercise_choice).try(:choice_position).present?
+                answer_choice_array.push(a&.exercise_choice&.choice_position) #学生答案的位置
+              end
             end
-            user_answer_content = answer_choice_array.sort
+            user_answer_content = answer_choice_array.reject(&:blank?).sort
             standard_answer = @exercise_question.exercise_standard_answers.pluck(:exercise_choice_id).sort
             if standard_answer.size == 1  # 老数据需要判断学生答题是否正确, 正确取原题得分，否则是0分
               standard_answer = standard_answer.first.to_s.split("").map(&:to_i).sort