onos6217-removing null pointer dereference

Change-Id: Idca13201ed344e6c102538030070e4a4ba024291
diff --git a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHandler.java b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHandler.java
index 07ecce2..b399fdf 100644
--- a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHandler.java
+++ b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHandler.java
@@ -185,7 +185,7 @@
         if (osNet == null || Strings.isNullOrEmpty(osNet.getProviderSegID())) {
             final String error = String.format(
                     ERR_SET_FLOWS + "Failed to get VNI for %s",
-                    instPort, osNet.getName());
+                    instPort, osNet == null ? "<none>" : osNet.getName());
             throw new IllegalStateException(error);
         }
         return Long.valueOf(osNet.getProviderSegID());