fix error when adding volt tenant
diff --git a/xos/tosca/resources/VOLTTenant.py b/xos/tosca/resources/VOLTTenant.py
index c9eceb4..20c4dfb 100644
--- a/xos/tosca/resources/VOLTTenant.py
+++ b/xos/tosca/resources/VOLTTenant.py
@@ -35,7 +35,9 @@
         provider_service = args.get("provider_service", None)
         service_specific_id = args.get("service_specific_id", None)
         if (provider_service) and (service_specific_id):
-            return [ self.get_xos_object(VOLTTenant, kind=VOLT_KIND, provider_service=provider_service, service_specific_id=service_specific_id) ]
+            existing_obj = self.get_xos_object(VOLTTenant, kind=VOLT_KIND, provider_service=provider_service, service_specific_id=service_specific_id, throw_exception=False)
+            if existing_obj:
+                return [ existing_obj ]
         return []
 
     def postprocess(self, obj):