Program: 32576
Project: 32576
Buggy source:
@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;
  }
  if (args.length < 2) {
    sender.sendMessage(messages.generalNoNickGiven);
    return;
  }
  if (!UserUtils.playedBefore(args[1])) {
    sender.sendMessage(messages.generalNotPlayedBefore);
    return;
  }
  User user=User.get(args[1]);
  if (user.hasGuild()) {
    sender.sendMessage(messages.generalUserHasGuild);
    return;
  }
  Guild guild=GuildUtils.byTag(args[0]);
  if (guild == null) {
    sender.sendMessage(messages.generalNoGuildFound);
    return;
  }
  User admin=(sender instanceof Player) ? User.get(sender.getName()) : null;
  if (!SimpleEventHandler.handle(new GuildMemberJoinEvent(admin == null ? EventCause.CONSOLE : EventCause.ADMIN,admin,guild,user))) {
    return;
  }
  guild.addMember(user);
  user.setGuild(guild);
  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",user.getName());
  Player player=user.getPlayer();
  Player owner=guild.getOwner().getPlayer();
  if (player != null) {
    player.sendMessage(translator.translate(messages.joinToMember));
  }
  if (owner != null) {
    owner.sendMessage(translator.translate(messages.joinToOwner));
  }
  Bukkit.broadcastMessage(translator.translate(messages.broadcastJoin));
}

Fixed version (ground truth):
@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;
  }
  if (args.length < 2) {
    sender.sendMessage(messages.generalNoNickGiven);
    return;
  }
  if (!UserUtils.playedBefore(args[1])) {
    sender.sendMessage(messages.generalNotPlayedBefore);
    return;
  }
  User user=User.get(args[1]);
  if (user.hasGuild()) {
    sender.sendMessage(messages.generalUserHasGuild);
    return;
  }
  Guild guild=GuildUtils.getByTag(args[0]);
  if (guild == null) {
    sender.sendMessage(messages.generalNoGuildFound);
    return;
  }
  User admin=(sender instanceof Player) ? User.get(sender.getName()) : null;
  if (!SimpleEventHandler.handle(new GuildMemberJoinEvent(admin == null ? EventCause.CONSOLE : EventCause.ADMIN,admin,guild,user))) {
    return;
  }
  guild.addMember(user);
  user.setGuild(guild);
  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",user.getName());
  Player player=user.getPlayer();
  Player owner=guild.getOwner().getPlayer();
  if (player != null) {
    player.sendMessage(translator.translate(messages.joinToMember));
  }
  if (owner != null) {
    owner.sendMessage(translator.translate(messages.joinToOwner));
  }
  Bukkit.broadcastMessage(translator.translate(messages.broadcastJoin));
}