新增数处理null兼容老的接口

ie-admin/src/main/java/com/ruoyi/web/service/ExamService.java

@@ -571,7 +571,7 @@ public class ExamService {
             up.setStatus(PaperStatus.Valid.getVal());
             paperMapper.updateLearnPaper(up);
         }
-        List<String> types = questionType.equals(0)
+        List<String> types = (null == questionType || questionType.equals(0))
                 ? Arrays.stream(QuestionType.values()).map(QuestionType::getTitle).collect(Collectors.toList())
                 : Lists.newArrayList(QuestionType.Single.getTitle(), QuestionType.Judgment.getTitle());
         List<LearnPaperQuestion> pqList = paperService.getQuestionsByRandom(studentId,  15, useKnowledgeIds, types, 0);