check if user exists

src/messaging.js

@@ -320,7 +320,17 @@ var db = require('./database'),
 	};
 
 	Messaging.markUnread = function(uid, toUid, callback) {
-		db.sortedSetAdd('uid:' + uid + ':chats:unread', Date.now(), toUid, callback);
+		async.waterfall([
+			function (next) {
+				user.exists(toUid, next);
+			},
+			function (exists, next) {
+				if (!exists) {
+					return next(new Error('[[error:no-user]]'));
+				}
+				db.sortedSetAdd('uid:' + uid + ':chats:unread', Date.now(), toUid, next);
+			}
+		], callback);
 	};
 
 	Messaging.notifyUser = function(fromuid, touid, messageObj) {

src/socket.io/modules.js

@@ -71,9 +71,12 @@ SocketModules.chats.canMessage = function(socket, toUid, callback) {
 
 SocketModules.chats.markRead = function(socket, touid, callback) {
 	Messaging.markRead(socket.uid, touid, function(err) {
-		if (!err) {
-			Messaging.pushUnreadCount(socket.uid);
+		if (err) {
+			return callback(err);
 		}
+
+		Messaging.pushUnreadCount(socket.uid);
+		callback();
 	});
 };