1、服务指标逻辑调整；

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

@@ -180,7 +180,7 @@ public class StudentServeServiceImpl implements StudentServeService {
                 long haveSubmitTimes = studentExercises.stream().filter(e->Objects.nonNull(e.getSubmitTime())).count();
                 if(replyNum>0&&haveSubmitTimes>0){
                     Date lastSubmitTime = studentExercises.stream().filter(e->Objects.nonNull(e.getSubmitTime())).max(Comparator.comparing(ExtracurricularExercisesReply::getSubmitTime)).get().getSubmitTime();
-                    if(lastSubmitTime.after(studentExtracurricularExercisesSituation.getLastSubmitTime())){
+                    if(Objects.isNull(studentExtracurricularExercisesSituation.getLastSubmitTime())||lastSubmitTime.after(studentExtracurricularExercisesSituation.getLastSubmitTime())){
                         studentExtracurricularExercisesSituation.setLastSubmitTime(lastSubmitTime);
                     }
                 }