fix:null

cooleshow-user/user-biz/src/main/java/com/yonge/cooleshow/biz/dal/service/impl/ActivityRewardServiceImpl.java

@@ -157,7 +157,7 @@ public class ActivityRewardServiceImpl extends ServiceImpl<ActivityRewardDao, Ac
     @Transactional(rollbackFor = Exception.class)
     public List<Long> sendReward(Long userId, Long activityId) {
         if (userRewarded(userId, activityId)) {
-            return null;
+            return new ArrayList<>();
         }
         ActivityPlan activityPlan = activityPlanService.getById(activityId);
         if (activityPlan == null) {