Enhanced flow list command to be more parsable and to use sorted devices list.
Fixed NPE.
diff --git a/core/net/src/main/java/org/onlab/onos/net/intent/impl/ObjectiveTracker.java b/core/net/src/main/java/org/onlab/onos/net/intent/impl/ObjectiveTracker.java
index 820668e..d84c367 100644
--- a/core/net/src/main/java/org/onlab/onos/net/intent/impl/ObjectiveTracker.java
+++ b/core/net/src/main/java/org/onlab/onos/net/intent/impl/ObjectiveTracker.java
@@ -113,7 +113,7 @@
         @Override
         public void run() {
             if (event.reasons() == null) {
-                delegate.triggerCompile(null, true);
+                delegate.triggerCompile(new HashSet<IntentId>(), true);
 
             } else {
                 Set<IntentId> toBeRecompiled = new HashSet<>();