Sonar suggestions - fixes to potential null pointer dereferences

Change-Id: I4e350a9d72a9322971d5d4f831f1bdf167986b87
diff --git a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/RulePopulatorUtil.java b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/RulePopulatorUtil.java
index 07a808d..5dbf7a7 100644
--- a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/RulePopulatorUtil.java
+++ b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/RulePopulatorUtil.java
@@ -98,6 +98,10 @@
             return null;
         }
 
+        if (device == null) {
+            return null;
+        }
+
         ExtensionTreatmentResolver resolver = device.as(ExtensionTreatmentResolver.class);
         ExtensionTreatment treatment = resolver.getExtensionInstruction(NICIRA_SET_TUNNEL_DST.type());
         try {