Merge branch 'fix-exam-paper-view-permission' into 'Release'

fix:考试开始前学生正常进入，拿到空的PaperVO







See merge request !1335

mooctest-site-server/src/main/java/cn/iselab/mooctest/site/web/ctrl/PaperController.java

@@ -72,7 +72,7 @@ public class PaperController extends BaseSearchController{
             if (!isAdmin && !isExamOwner) {
                 boolean isExamOwnerOrParticipant = examLogic.checkTaskViewPermission(userId, examId);
                 if (exam.getStatus().equals(Exam.STATUS_UPCOMING)) {
-                    throw new UnauthenticatedException("forbidden");
+                    return new PaperVO();
                 } else if (!isExamOwnerOrParticipant) {
                     throw new UnauthenticatedException("forbidden");
                 }