Passing an empty list instead of null to improve null-safety

Change-Id: I6bef6c4c263a369ed49ea1da12c23528a56dd2c8

@@ -16,6 +16,7 @@
 package org.onosproject.net.intent.impl;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -66,7 +67,7 @@ public class SinglePointToMultiPointIntentCompiler
         Intent result = new LinkCollectionIntent(intent.appId(),
                                                  intent.selector(),
                                                  intent.treatment(), links,
-                                                 intent.egressPoints(), null);
+                                                 intent.egressPoints(), Collections.emptyList());
 
         return Arrays.asList(result);
     }