Code changes for adding NONE as subcategory

Change-Id: Id2e239056f5be7fd33941fb76e8cfd6a30a2e162
diff --git a/pkg/events/events_proxy.go b/pkg/events/events_proxy.go
index a4b12f7..c4014ee 100644
--- a/pkg/events/events_proxy.go
+++ b/pkg/events/events_proxy.go
@@ -78,6 +78,8 @@
 	header.Category = category
 	if subCategory != nil {
 		header.SubCategory = *subCategory
+	} else {
+		header.SubCategory = voltha.EventSubCategory_NONE
 	}
 	header.Type = eventType
 	header.TypeVersion = eventif.EventTypeVersion