add default group

backstage-service/src/main/resources/bootstrap.properties

@@ -36,6 +36,7 @@ dubbo.cloud.subscribed-services=
 dubbo.application.qos.enable=false
 dubbo.application.qos.port=28111
 dubbo.application.qos.accept.foreign.ip=false
+dubbo.registry.group=
 
 dubbo.reference.com.foo.BarService.check=false
 dubbo.reference.check=false