#vulnerable code 
                                @Override
    public void execute(CommandSender sender, String[] args) {
        MessagesConfig messages = Messages.getInstance();

        if (args.length < 1) {
            sender.sendMessage(messages.generalNoTagGiven);
            return;
        }

        if (!GuildUtils.tagExists(args[0])) {
            sender.sendMessage(messages.generalNoGuildFound);
            return;
        }

        Guild guild = GuildUtils.byTag(args[0]);
        if (!guild.isBanned()) {
            sender.sendMessage(messages.adminGuildNotBanned);
            return;
        }

        BanUtils.unban(guild);
        sender.sendMessage(messages.adminGuildUnban.replace("{GUILD}", guild.getName()));
        Bukkit.broadcastMessage(Messages.getInstance().broadcastUnban.replace("{GUILD}", guild.getName()).replace("{TAG}", guild.getTag()));
    } 
                            #location 16 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public void execute(CommandSender sender, String[] args) {
        MessagesConfig messages = Messages.getInstance();

        if (args.length < 1) {
            sender.sendMessage(messages.generalNoTagGiven);
            return;
        }

        Guild guild = GuildUtils.byTag(args[0]);

        if (guild == null) {
            sender.sendMessage(messages.generalNoGuildFound);
            return;
        }

        if (!guild.isBanned()) {
            sender.sendMessage(messages.adminGuildNotBanned);
            return;
        }

        BanUtils.unban(guild);

        MessageTranslator translator = new MessageTranslator()
                .register("{GUILD}", guild.getName())
                .register("{TAG}", guild.getName())
                .register("{ADMIN}", sender.getName());

        sender.sendMessage(translator.translate(messages.adminGuildUnban));
        Bukkit.broadcastMessage(translator.translate(messages.broadcastUnban));
    }