Couchbase lite Sync Warning

Question

I am new to couch base and I am using couchbaselite-1.4.0 for my JAVAFX application.

When I start the application, after few seconds, I am getting the below warning. And my database is not syncing with remote database anymore.

Dec 11, 2017 12:45:07 PM com.couchbase.lite.util.SystemLogger w
WARNING: Sync: Error converting lastSequence: null to long.  Using 0

My code is

Logger log = Logger.getLogger(DatabaseConfig.LOCAL_DATABASE);
    log.setLevel(Level.ALL);
    JavaContext context = new JavaContext();

    Manager manager = null;
    try {
        manager = new Manager(context, Manager.DEFAULT_OPTIONS);
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        if (manager != null) {
            database = manager.getDatabase(DatabaseConfig.LOCAL_DATABASE);

            // Create replicators to push & pull changes to & from Sync Gateway
            URL url = null;
            try {
                url = new URL(DatabaseConfig.REMOTE_DATABASE);
            } catch (MalformedURLException e) {
                e.printStackTrace();
            }

            initSync(url);

            //Initiating Views
            initViews();
        } else {
            Check.log(this,"initDatabase","manager is null");
        }
    } catch (CouchbaseLiteException e) {
        e.printStackTrace();
    }

}

private void initSync(URL url) {
    List<String> pullChannels = Arrays.asList(ChannelType.ITEM, ChannelType.BILL, ChannelType.CATEGORY, ChannelType.PURCHASE_BILL);
    Check.temp("pullChannels: "+pullChannels);
    if (url != null && pullChannels.size() > 0) {

        Authenticator authenticator = AuthenticatorFactory.createBasicAuthenticator(AppConfig.ADMIN_ID, AppConfig.ADMIN_PASSWORD);
        Check.temp("admin details: "+AppConfig.ADMIN_ID+" : "+AppConfig.ADMIN_PASSWORD);

        Replication push = database.createPushReplication(url);
        Replication pull = database.createPullReplication(url);

        pull.setChannels(pullChannels);

        push.setContinuous(true);
        pull.setContinuous(true);

        push.setAuthenticator(authenticator);
        pull.setAuthenticator(authenticator);

        push.start();
        pull.start();

        Check.temp("status: "+push.getStatus()+" x "+pull.getStatus());
    } else {
        Check.log(this,"initSync","url or channels is null");
    }
}

Please help me from this