Merge pull request #1140 from shuxiaoyuan/fix-update-time

bugfix：目录订阅收到更新事件时，sql字段update_time为空导致的报错

src/main/java/com/genersoft/iot/vmp/service/impl/DeviceChannelServiceImpl.java

@@ -243,6 +243,10 @@ public class DeviceChannelServiceImpl implements IDeviceChannelService {
 
     @Override
     public void batchUpdateChannel(List<DeviceChannel> channels) {
+        String now = DateUtil.getNow();
+        for (DeviceChannel channel : channels) {
+            channel.setUpdateTime(now);
+        }
         channelMapper.batchUpdate(channels);
         for (DeviceChannel channel : channels) {
             if (channel.getParentId() != null) {