minor fix to prevent err when trying to mark null nid

src/messaging.js

@@ -92,7 +92,7 @@ var db = require('./database'),
 				return callback(err);
 			}
 
-			if (!mids || !mids.length) {
+			if (!Array.isArray(mids) || !mids.length) {
 				return callback(null, []);
 			}
 

src/notifications.js

@@ -214,7 +214,7 @@ var async = require('async'),
 
 	Notifications.markRead = function(nid, uid, callback) {
 		callback = callback || function() {};
-		if (!parseInt(uid, 10)) {
+		if (!parseInt(uid, 10) || !parseInt(nid, 10)) {
 			return callback();
 		}