3.4.5 update-20250423，bug修改

teachcloud-mark/src/main/java/com/qmth/teachcloud/mark/service/impl/MarkServiceImpl.java

@@ -1152,7 +1152,7 @@ public class MarkServiceImpl implements MarkService {
         while (task == null) {
             if (questionModel.equals(QuestionModel.SINGLE)) {
                 MarkQuestion markQuestion = markQuestionService.getById(questionId);
-                if (!markQuestion.getPersonTask()) {
+                if (markQuestion == null || !markQuestion.getPersonTask()) {
                     break;
                 }
                 Set<Long> questions = new HashSet<>(Arrays.asList(questionId));