Program: 32575
Project: 32575
Buggy source:
@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.joinHasGuild);
    return;
  }
  List<InvitationList.Invitation> invitations=InvitationList.getInvitationsFor(player);
  if (invitations.size() == 0) {
    player.sendMessage(messages.joinHasNotInvitation);
    return;
  }
  if (args.length < 1) {
    String guildNames=StringUtils.toString(InvitationList.getInvitationGuildNames(player),false);
    for (    String msg : messages.joinInvitationList) {
      player.sendMessage(msg.replace("String_Node_Str",guildNames));
    }
    return;
  }
  String tag=args[0];
  Guild guild=Guild.get(tag);
  if (guild == null) {
    player.sendMessage(messages.joinTagExists);
    return;
  }
  if (!InvitationList.hasInvitationFrom(player,GuildUtils.byTag(tag))) {
    player.sendMessage(messages.joinHasNotInvitationTo);
    return;
  }
  List<ItemStack> requiredItems=Settings.getConfig().joinItems;
  for (  ItemStack requiredItem : requiredItems) {
    if (player.getInventory().containsAtLeast(requiredItem,requiredItem.getAmount())) {
      continue;
    }
    String msg=ItemUtils.translatePlaceholder(messages.joinItems,requiredItems,requiredItem);
    player.sendMessage(msg);
    return;
  }
  if (!SimpleEventHandler.handle(new GuildMemberAcceptInviteEvent(EventCause.USER,user,guild,user))) {
    return;
  }
  InvitationList.expireInvitation(guild,player);
  if (!SimpleEventHandler.handle(new GuildMemberJoinEvent(EventCause.USER,user,guild,user))) {
    return;
  }
  guild.addMember(user);
  user.setGuild(guild);
  player.getInventory().removeItem(ItemUtils.toArray(requiredItems));
  IndependentThread.action(ActionType.PREFIX_GLOBAL_ADD_PLAYER,user.getOfflineUser());
  MessageTranslator translator=new MessageTranslator().register("String_Node_Str",guild.getName()).register("String_Node_Str",guild.getTag()).register("String_Node_Str",player.getName());
  player.sendMessage(translator.translate(messages.joinToMember));
  Bukkit.broadcastMessage(translator.translate(messages.broadcastJoin));
  Player owner=guild.getOwner().getPlayer();
  if (owner != null) {
    owner.sendMessage(translator.translate(messages.joinToOwner));
  }
}

Fixed version (ground truth):
@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.joinHasGuild);
    return;
  }
  List<InvitationList.Invitation> invitations=InvitationList.getInvitationsFor(player);
  if (invitations.size() == 0) {
    player.sendMessage(messages.joinHasNotInvitation);
    return;
  }
  if (args.length < 1) {
    String guildNames=StringUtils.toString(InvitationList.getInvitationGuildNames(player),false);
    for (    String msg : messages.joinInvitationList) {
      player.sendMessage(msg.replace("String_Node_Str",guildNames));
    }
    return;
  }
  String tag=args[0];
  Guild guild=GuildUtils.getByTag(tag);
  if (guild == null) {
    player.sendMessage(messages.joinTagExists);
    return;
  }
  if (!InvitationList.hasInvitationFrom(player,GuildUtils.getByTag(tag))) {
    player.sendMessage(messages.joinHasNotInvitationTo);
    return;
  }
  List<ItemStack> requiredItems=Settings.getConfig().joinItems;
  for (  ItemStack requiredItem : requiredItems) {
    if (player.getInventory().containsAtLeast(requiredItem,requiredItem.getAmount())) {
      continue;
    }
    String msg=ItemUtils.translatePlaceholder(messages.joinItems,requiredItems,requiredItem);
    player.sendMessage(msg);
    return;
  }
  if (!SimpleEventHandler.handle(new GuildMemberAcceptInviteEvent(EventCause.USER,user,guild,user))) {
    return;
  }
  InvitationList.expireInvitation(guild,player);
  if (!SimpleEventHandler.handle(new GuildMemberJoinEvent(EventCause.USER,user,guild,user))) {
    return;
  }
  guild.addMember(user);
  user.setGuild(guild);
  player.getInventory().removeItem(ItemUtils.toArray(requiredItems));
  IndependentThread.action(ActionType.PREFIX_GLOBAL_ADD_PLAYER,user.getOfflineUser());
  MessageTranslator translator=new MessageTranslator().register("String_Node_Str",guild.getName()).register("String_Node_Str",guild.getTag()).register("String_Node_Str",player.getName());
  player.sendMessage(translator.translate(messages.joinToMember));
  Bukkit.broadcastMessage(translator.translate(messages.broadcastJoin));
  Player owner=guild.getOwner().getPlayer();
  if (owner != null) {
    owner.sendMessage(translator.translate(messages.joinToOwner));
  }
}