Sonar fixes

Rule: Use isEmpty() to check whether the collection is empty or not.

Change-Id: Ib5ab56b2263623b297db56c5cac2c2ee80e12725
diff --git a/providers/openflow/group/src/main/java/org/onosproject/provider/of/group/impl/GroupBucketEntryBuilder.java b/providers/openflow/group/src/main/java/org/onosproject/provider/of/group/impl/GroupBucketEntryBuilder.java
index 1ba438d..58cf18e 100644
--- a/providers/openflow/group/src/main/java/org/onosproject/provider/of/group/impl/GroupBucketEntryBuilder.java
+++ b/providers/openflow/group/src/main/java/org/onosproject/provider/of/group/impl/GroupBucketEntryBuilder.java
@@ -119,7 +119,7 @@
         TrafficTreatment.Builder builder = DefaultTrafficTreatment.builder();
 
         // If this is a drop rule
-        if (actions.size() == 0) {
+        if (actions.isEmpty()) {
             builder.drop();
             return builder.build();
         }