Generate kubevirt network from NetworkAttachmentDefinition CRD

Change-Id: Id16d2a8471b75500e968a96b5597a22a9972e0b0
diff --git a/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/DefaultKubevirtNetwork.java b/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/DefaultKubevirtNetwork.java
index 97808bb..970c0eb 100644
--- a/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/DefaultKubevirtNetwork.java
+++ b/apps/kubevirt-networking/api/src/main/java/org/onosproject/kubevirtnetworking/api/DefaultKubevirtNetwork.java
@@ -107,7 +107,11 @@
 
     @Override
     public Set<KubevirtHostRoute> hostRoutes() {
-        return ImmutableSet.copyOf(hostRoutes);
+        if (hostRoutes == null || hostRoutes.size() == 0) {
+            return ImmutableSet.of();
+        } else {
+            return ImmutableSet.copyOf(hostRoutes);
+        }
     }
 
     @Override