fixed check

src/main/java/org/gcube/portal/social/networking/ws/methods/v2/Notifications.java

@@ -346,7 +346,7 @@ public class Notifications {
 						status = Status.NOT_ACCEPTABLE;
 						logger.error("Username not found", e);
 						responseBean.setSuccess(false);
-						responseBean.setMessage("Username not found " + userIdToNotify);
+						responseBean.setMessage("Username not found, received: " + userIdToNotify);
 						return Response.status(status).entity(responseBean).build();
 					}
 					deliveryResult 	= notifyWorkspaceEvent(event, nm, username2Notify);