Fix: resolve a NPE on updating VM port information

Change-Id: I2c23559d1c7cb1aad2bb8f6ff5a536c23620a37c
diff --git a/apps/kubevirt-networking/app/src/main/java/org/onosproject/kubevirtnetworking/impl/KubevirtVmWatcher.java b/apps/kubevirt-networking/app/src/main/java/org/onosproject/kubevirtnetworking/impl/KubevirtVmWatcher.java
index f13d5b1..f4f0156 100644
--- a/apps/kubevirt-networking/app/src/main/java/org/onosproject/kubevirtnetworking/impl/KubevirtVmWatcher.java
+++ b/apps/kubevirt-networking/app/src/main/java/org/onosproject/kubevirtnetworking/impl/KubevirtVmWatcher.java
@@ -289,7 +289,8 @@
                     if (!existing.ipAddress().equals(ip)) {
                         updatedPort = updatedPort.updateIpAddress(ip);
                     }
-                    if (!port.securityGroups().equals(sgs) || !port.ipAddress().equals(ip)) {
+                    if (!existing.securityGroups().equals(sgs) ||
+                            !existing.ipAddress().equals(ip)) {
                         portAdminService.updatePort(updatedPort);
                     }
                 }