fix

mec-biz/src/main/java/com/ym/mec/biz/service/impl/StudentCourseHomeworkServiceImpl.java

@@ -989,7 +989,9 @@ public class StudentCourseHomeworkServiceImpl extends BaseServiceImpl<Long, Stud
         } else if (studentLessonTrainingDetail.getTrainingStatus() == StandardEnum.NOT_START) {
             studentLessonTrainingDetail.setTrainingStatus(StandardEnum.NOT_STANDARD);
         }
-        studentLessonTrainingDetail.setFileJson(JSON.toJSONString(record.getFileJson()));
+        if (CollectionUtils.isNotEmpty(record.getFileJson())) {
+            studentLessonTrainingDetail.setFileJson(JSON.toJSONString(record.getFileJson()));
+        }
         studentLessonTrainingDetail.setUpdateTime(new Date());
         studentLessonTrainingDetailService.updateById(studentLessonTrainingDetail);