Player Interact Event Error

@EventHandler
    public void playerInteract(PlayerInteractEvent event)
    {
        Player player = event.getPlayer();
        Action action = event.getAction();
        Material block = event.getClickedBlock().getType();
        if(block != null)
        {
            if(action == Action.LEFT_CLICK_AIR)
            {
                event.setCancelled(true);
            }
            if(action == Action.LEFT_CLICK_BLOCK)
            {
                event.setCancelled(true);
            }
            if(action == Action.RIGHT_CLICK_AIR)
            {
                event.setCancelled(true);
            }
            if(action == Action.RIGHT_CLICK_BLOCK)
            {
                Sign sign = (Sign)event.getClickedBlock().getState();
                String line1 = sign.getLine(1);

                if(line1.contains("[JoinGame]") && Main.plugin.Players.size() < Main.maxPlayers && Main.isWorldGenerated == true)
                {
                    if(Main.plugin.InGameQueue.containsKey(player))
                    {
                        player.sendMessage(ReferenceStrings.errorJoin1);
                    }
                    else if(Main.GameStarted == false)
                    {
                        if(Main.plugin.Players.size() > 10)
                        {
                            Teleport.VotingAndToolSelection(player);
                            Main.plugin.InGameQueue.put(player, null);
                            Main.plugin.Players.put(player, null);
                            Bukkit.broadcastMessage(ChatColor.LIGHT_PURPLE + "[MobAPA] " + ChatColor.GREEN + player.getName() + " has joined the Game. " + Main.plugin.Players.size() + "/" + Main.maxPlayers + " Joined");
                        }
                        else
                        {
                            Teleport.VotingAndToolSelection(player);
                            Main.plugin.InGameQueue.put(player, null);
                            Main.plugin.Players.put(player, null);
                            Bukkit.broadcastMessage(ChatColor.LIGHT_PURPLE + "[MobAPA] " + ChatColor.GREEN + player.getName() + " has joined the Game. We need 10 players to start! There are currently: " + Main.plugin.Players.size() + "/" + Main.maxPlayers + " Joined");
                            System.out.println(Main.plugin.Players.size());
                            if(Main.plugin.Players.size() == 10)
                            {
                                CountDown.StartCountDownTimer(player);
                            }
                        }
                    }
                    else if(Main.GameStarted == true)
                    {
                        player.sendMessage(ReferenceStrings.errorJoin2);
                    }
                }
                else
                {
                    if(Main.isWorldGenerated == false)
                    {
                        player.sendMessage(ReferenceStrings.worldIsNotGenerated);
                    }
                    else
                    {
                        player.sendMessage(ReferenceStrings.errorJoin3);
                    }
                }
            }
        }
        else
        {
            event.setCancelled(true);
        }
    }