#vulnerable code 
                                @EventHandler
    public void onJoin(PlayerJoinEvent e) {
        Player player = e.getPlayer();
        User user = User.get(player);

        if (user == null) {
            user = User.create(player);
        }

        user.updateReference(player);
        PluginConfiguration config = FunnyGuilds.getInstance().getPluginConfiguration();

        if (config.playerListEnable && ! AbstractTablist.hasTablist(player)) {
            AbstractTablist.createTablist(config.playerList, config.playerListHeader, config.playerListFooter, config.playerListPing, player);
        }

        UserCache cache = user.getCache();

        if (cache.getScoreboard() == null) {
            cache.setScoreboard(Bukkit.getScoreboardManager().getNewScoreboard());
        }

        if (cache.getIndividualPrefix() == null && config.guildTagEnabled) {
            IndividualPrefix prefix = new IndividualPrefix(user);
            prefix.initialize();

            cache.setIndividualPrefix(prefix);
        }

        ConcurrencyManager concurrencyManager = FunnyGuilds.getInstance().getConcurrencyManager();
        concurrencyManager.postRequests(
                new PrefixGlobalUpdatePlayer(player),
                new DummyGlobalUpdateUserRequest(user),
                new RankUpdateUserRequest(user)
        );

        this.plugin.getServer().getScheduler().runTaskLaterAsynchronously(this.plugin, () -> {
            PacketExtension.registerPlayer(player);
            FunnyGuildsVersion.isNewAvailable(player, false);

            Region region = RegionUtils.getAt(player.getLocation());
            if (region == null || region.getGuild() == null) {
                return;
            }
            
            if (config.createEntityType != null) {
                GuildEntityHelper.spawnGuildHeart(region.getGuild(), player);
            }
        }, 30L);
    } 
                            #location 19 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @EventHandler
    public void onJoin(PlayerJoinEvent e) {
        Player player = e.getPlayer();
        User user = User.get(player);

        if (user == null) {
            user = User.create(player);
        } else {
            if (! user.getName().equals(player.getName())) {
                user.setName(player.getName());
            }
        }

        user.updateReference(player);
        PluginConfiguration config = FunnyGuilds.getInstance().getPluginConfiguration();

        if (config.playerListEnable && ! AbstractTablist.hasTablist(player)) {
            AbstractTablist.createTablist(config.playerList, config.playerListHeader, config.playerListFooter, config.playerListPing, player);
        }

        UserCache cache = user.getCache();

        if (cache.getScoreboard() == null) {
            cache.setScoreboard(Bukkit.getScoreboardManager().getNewScoreboard());
        }

        if (cache.getIndividualPrefix() == null && config.guildTagEnabled) {
            IndividualPrefix prefix = new IndividualPrefix(user);
            prefix.initialize();

            cache.setIndividualPrefix(prefix);
        }

        ConcurrencyManager concurrencyManager = FunnyGuilds.getInstance().getConcurrencyManager();
        concurrencyManager.postRequests(
                new PrefixGlobalUpdatePlayer(player),
                new DummyGlobalUpdateUserRequest(user),
                new RankUpdateUserRequest(user)
        );

        this.plugin.getServer().getScheduler().runTaskLaterAsynchronously(this.plugin, () -> {
            PacketExtension.registerPlayer(player);
            FunnyGuildsVersion.isNewAvailable(player, false);

            Region region = RegionUtils.getAt(player.getLocation());
            if (region == null || region.getGuild() == null) {
                return;
            }
            
            if (config.createEntityType != null) {
                GuildEntityHelper.spawnGuildHeart(region.getGuild(), player);
            }
        }, 30L);
    }