Preventing NPEs in stores via notifyDelegate

Change-Id: I1c4b83c6a03b1f69a3ea1329724a7208d47cefa4
diff --git a/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java b/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
index faf7e50..c81d7ab 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
@@ -1823,7 +1823,7 @@
             if (event.type() == PUT) {
                 Device device = devices.get(event.key());
                 if (device != null) {
-                    delegate.notify(new DeviceEvent(PORT_STATS_UPDATED, device));
+                    notifyDelegate(new DeviceEvent(PORT_STATS_UPDATED, device));
                 }
             }
         }