fix: 修复增加字段带来的创建评测失败的bug

src/main/java/com/nju/edu/eval/service/serviceImpl/ExamServiceImpl.java

@@ -51,6 +51,7 @@ public class ExamServiceImpl implements ExamService {
         Exam exam = new Exam(examVO.getExamName(), examVO.getPosition(),
                                                       examVO.getSkills(), examVO.getStartTime(),
                                                       examVO.getEndTime(), examVO.getComment(), user);
+        exam.setIsHidden(false);
         // 只有非公开的考试才需要邀请码
         if (!examVO.getIsPublic()) {
             exam.setIsPublic(0);