fix bugs

stmms-biz/src/main/java/cn/com/qmth/stmms/biz/exam/service/impl/ExamStudentServiceImpl.java

@@ -1048,6 +1048,8 @@ public class ExamStudentServiceImpl extends BaseQueryService<ExamStudent> implem
     @Override
     public ExamStudent randomStudent(Integer examId, String code) {
         ExamStudentSearchQuery query = new ExamStudentSearchQuery();
+        query.setExamId(examId);
+        query.setSubjectCode(code);
         query.setAbsent(false);
         query.setUpload(true);
         query.setBreach(false);