add default group

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

@@ -57,6 +57,7 @@ dubbo.consumer.check=false
 dubbo.registry.check=false
 dubbo.registry.register=true
 dubbo.application.name=${spring.application.name}-dubbo
+dubbo.registry.group=
 
 dubbo.service.min.thread.pool.size=200
 dubbo.service.max.thread.pool.size=200