Update joi validation to reject empty Notification array on createMonitor

Server/validation/joi.js

@@ -222,7 +222,7 @@ const createMonitorBodyValidation = joi.object({
 	url: joi.string().required(),
 	isActive: joi.boolean(),
 	interval: joi.number(),
-	notifications: joi.array().items(joi.object()),
+	notifications: joi.array().items(joi.object()).min(1),
 });
 
 const editMonitorBodyValidation = joi.object({