Fix for ONOS-4618.

Change-Id: If36e50d64a53e8c49aaafabe195bc057e7e17b74
diff --git a/core/store/dist/src/main/java/org/onosproject/store/link/impl/ECLinkStore.java b/core/store/dist/src/main/java/org/onosproject/store/link/impl/ECLinkStore.java
index fbaabd6..d93672e 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/link/impl/ECLinkStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/link/impl/ECLinkStore.java
@@ -261,9 +261,9 @@
             linkDescriptions.compute(internalLinkKey, (k, v) -> createOrUpdateLinkInternal(v, linkDescription));
             return refreshLinkCache(linkKey);
         } else {
-            // Only forward for ConfigProvider
+            // Only forward for ConfigProvider or NullProvider
             // Forwarding was added as a workaround for ONOS-490
-            if (!providerId.scheme().equals("cfg")) {
+            if (!providerId.scheme().equals("cfg") && !providerId.scheme().equals("null")) {
                 return null;
             }
             // Temporary hack for NPE (ONOS-1171).