#vulnerable code 
                                @Override
    public void execute(CommandSender sender, String[] args) {
        MessagesConfig m = Messages.getInstance();
        Player p = (Player) sender;
        User u = User.get(p);

        if (!u.hasGuild()) {
            p.sendMessage(m.kickHasNotGuild);
            return;
        }

        if (!u.isOwner() && !u.isDeputy()) {
            p.sendMessage(m.kickIsNotOwner);
            return;
        }

        if (args.length < 1) {
            p.sendMessage(m.kickPlayer);
            return;
        }

        User uk = User.get(args[0]);
        OfflineUser up = uk.getOfflineUser();

        if (!uk.hasGuild()) {
            p.sendMessage(m.kickToHasNotGuild);
            return;
        }

        if (!u.getGuild().equals(uk.getGuild())) {
            p.sendMessage(m.kickOtherGuild);
            return;
        }

        if (uk.isOwner()) {
            p.sendMessage(m.kickOwner);
            return;
        }

        Guild guild = u.getGuild();
        IndependentThread.action(ActionType.PREFIX_GLOBAL_REMOVE_PLAYER, up);

        guild.removeMember(uk);
        uk.removeGuild();

        if (up.isOnline()) {
            IndependentThread.action(ActionType.PREFIX_GLOBAL_UPDATE_PLAYER, p);
        }

        p.sendMessage(m.kickToOwner.replace("{PLAYER}", uk.getName()));

        Player pk = uk.getPlayer();
        if (pk != null) {
            pk.sendMessage(m.kickToPlayer.replace("{GUILD}", guild.getName()));
        }

        Bukkit.broadcastMessage(m.broadcastKick.replace("{PLAYER}", uk.getName()).replace("{GUILD}", guild.getName()).replace("{TAG}", guild.getTag()));
    } 
                            #location 13 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public void execute(CommandSender sender, String[] args) {
        MessagesConfig messages = Messages.getInstance();
        Player player = (Player) sender;
        User user = User.get(player);

        if (!user.hasGuild()) {
            player.sendMessage(messages.kickHasNotGuild);
            return;
        }

        if (!user.isOwner() && !user.isDeputy()) {
            player.sendMessage(messages.kickIsNotOwner);
            return;
        }

        if (args.length < 1) {
            player.sendMessage(messages.kickPlayer);
            return;
        }

        User formerUser = User.get(args[0]);
        OfflineUser formerOffline = formerUser.getOfflineUser();

        if (!formerUser.hasGuild()) {
            player.sendMessage(messages.kickToHasNotGuild);
            return;
        }

        if (!user.getGuild().equals(formerUser.getGuild())) {
            player.sendMessage(messages.kickOtherGuild);
            return;
        }

        if (formerUser.isOwner()) {
            player.sendMessage(messages.kickOwner);
            return;
        }

        Guild guild = user.getGuild();
        IndependentThread.action(ActionType.PREFIX_GLOBAL_REMOVE_PLAYER, formerOffline);

        guild.removeMember(formerUser);
        formerUser.removeGuild();

        if (formerOffline.isOnline()) {
            IndependentThread.action(ActionType.PREFIX_GLOBAL_UPDATE_PLAYER, player);
        }

        MessageTranslator translator = new MessageTranslator()
                .register("{PLAYER}", formerUser.getName())
                .register("{GUILD}", guild.getName())
                .register("{TAG}", guild.getTag());

        player.sendMessage(translator.translate(messages.kickToOwner));
        Bukkit.broadcastMessage(translator.translate(messages.broadcastKick));

        Player formerPlayer = formerUser.getPlayer();

        if (formerPlayer != null) {
            formerPlayer.sendMessage(translator.translate(messages.kickToPlayer));
        }
    }