#vulnerable code 
                                private void readMessage(Player player, LoginActionMessage message) {
        String playerName = message.getPlayerName();
        Type type = message.getType();

        InetSocketAddress address = player.getAddress();
        String id = '/' + address.getAddress().getHostAddress() + ':' + address.getPort();
        if (type == Type.LOGIN) {
            BukkitLoginSession playerSession = new BukkitLoginSession(playerName, true);
            playerSession.setVerified(true);
            plugin.getLoginSessions().put(id, playerSession);

            Bukkit.getScheduler().runTaskLaterAsynchronously(plugin, new ForceLoginTask(plugin.getCore(), player), 10L);
        } else if (type == Type.REGISTER) {
            Bukkit.getScheduler().runTaskLaterAsynchronously(plugin, () -> {
                AuthPlugin<Player> authPlugin = plugin.getCore().getAuthPluginHook();
                try {
                    //we need to check if the player is registered on Bukkit too
                    if (authPlugin == null || !authPlugin.isRegistered(playerName)) {
                        BukkitLoginSession playerSession = new BukkitLoginSession(playerName, false);
                        playerSession.setVerified(true);
                        plugin.getLoginSessions().put(id, playerSession);
                        new ForceLoginTask(plugin.getCore(), player).run();
                    }
                } catch (Exception ex) {
                    plugin.getLog().error("Failed to query isRegistered for player: {}", player, ex);
                }
            }, 10L);
        } else if (type == Type.CRACKED) {
            //we don't start a force login task here so update it manually
            plugin.getPremiumPlayers().put(player.getUniqueId(), PremiumStatus.CRACKED);
        }
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private void readMessage(Player player, LoginActionMessage message) {
        String playerName = message.getPlayerName();
        Type type = message.getType();

        InetSocketAddress address = player.getAddress();
        if (type == Type.LOGIN) {
            BukkitLoginSession playerSession = new BukkitLoginSession(playerName, true);
            playerSession.setVerified(true);
            plugin.putSession(address, playerSession);

            Bukkit.getScheduler().runTaskLaterAsynchronously(plugin, new ForceLoginTask(plugin.getCore(), player), 10L);
        } else if (type == Type.REGISTER) {
            Bukkit.getScheduler().runTaskLaterAsynchronously(plugin, () -> {
                AuthPlugin<Player> authPlugin = plugin.getCore().getAuthPluginHook();
                try {
                    //we need to check if the player is registered on Bukkit too
                    if (authPlugin == null || !authPlugin.isRegistered(playerName)) {
                        BukkitLoginSession playerSession = new BukkitLoginSession(playerName, false);
                        playerSession.setVerified(true);
                        plugin.putSession(address, playerSession);
                        new ForceLoginTask(plugin.getCore(), player).run();
                    }
                } catch (Exception ex) {
                    plugin.getLog().error("Failed to query isRegistered for player: {}", player, ex);
                }
            }, 10L);
        } else if (type == Type.CRACKED) {
            //we don't start a force login task here so update it manually
            plugin.getPremiumPlayers().put(player.getUniqueId(), PremiumStatus.CRACKED);
        }
    }