Fix one of the causes of ONOS-3954

Return statement was missing on an allocation failure

Change-Id: If6107462061ef56cd45ccb9e6d67d47f6aae9f43
diff --git a/core/net/src/main/java/org/onosproject/net/intent/impl/compiler/PathCompiler.java b/core/net/src/main/java/org/onosproject/net/intent/impl/compiler/PathCompiler.java
index b954305..50114ec 100644
--- a/core/net/src/main/java/org/onosproject/net/intent/impl/compiler/PathCompiler.java
+++ b/core/net/src/main/java/org/onosproject/net/intent/impl/compiler/PathCompiler.java
@@ -115,7 +115,7 @@
         List<ResourceAllocation> allocations =
                 creator.resourceService().allocate(intent.id(), ImmutableList.copyOf(resources));
         if (allocations.isEmpty()) {
-            Collections.emptyMap();
+            return Collections.emptyMap();
         }
 
         return vlanIds;