修复线上泵站问题

sms_water/src/main/java/com/huaxu/service/impl/OnlineMonitorImpl.java

@@ -899,7 +899,7 @@ public class OnlineMonitorImpl implements OnlineMonitorService {
     {
         List<AlarmDetailsVo> alarmDetailsVos =  onlineMonitorMapper.selectAlarmStatsInfo(dto);
         if (CollectionUtil.isEmpty(alarmDetailsVos)) {
-            return null;
+            return new ArrayList<>();
         }
         Map<Long, AlarmDetailsVo> dataMap = new HashMap<>();
         Long sendId  = null;