Handle an server getNotenameFromSocket referer undefined exception

lib/realtime.js

@@ -151,7 +151,11 @@ function getStatus(callback) {
 }
 
 function getNotenameFromSocket(socket) {
-    var hostUrl = url.parse(socket.handshake.headers.referer);
+    var referer = socket.handshake.headers.referer;
+    if (!referer) {
+        return socket.disconnect();
+    }
+    var hostUrl = url.parse(referer);
     var notename = hostUrl.pathname.split('/')[1];
     if (notename == config.featuresnotename) {
         return notename;