Ensure returning null on allocation failure

Change-Id: Ifdc5354b8b00ec4f87ed20a1b877abfe576c31ac
diff --git a/core/net/src/main/java/org/onosproject/net/intent/impl/compiler/OpticalConnectivityIntentCompiler.java b/core/net/src/main/java/org/onosproject/net/intent/impl/compiler/OpticalConnectivityIntentCompiler.java
index a4ed551..2941ddb 100644
--- a/core/net/src/main/java/org/onosproject/net/intent/impl/compiler/OpticalConnectivityIntentCompiler.java
+++ b/core/net/src/main/java/org/onosproject/net/intent/impl/compiler/OpticalConnectivityIntentCompiler.java
@@ -189,6 +189,7 @@
         List<ResourceAllocation> allocations = resourceService.allocate(intent.id(), lambdaResources);
         if (allocations.isEmpty()) {
             log.info("Resource allocation for {} failed (resource request: {})", intent, lambdaResources);
+            return null;
         }
 
         return minLambda;