Program: 38803
Project: 38803
Buggy source:
private boolean unregisterCommand(CommandSender sender,String[] args){
  if (sender instanceof Player) {
    Player player=(Player)sender;
    if (!xAuthPermissions.has(player,"String_Node_Str")) {
      xAuthMessages.send("String_Node_Str",player);
      return true;
    }
 else     if (args.length < 2) {
      xAuthMessages.send("String_Node_Str",player);
      return true;
    }
    String targetName=args[1];
    xAuthPlayer xPlayer=dataManager.getPlayer(targetName);
    if (!xPlayer.isRegistered()) {
      xAuthMessages.send("String_Node_Str",player,xPlayer.getPlayer());
      return true;
    }
    dataManager.deleteAccount(xPlayer);
    Player target=xPlayer.getPlayer();
    if (target != null) {
      plugin.createGuest(xPlayer);
      xAuthMessages.send("String_Node_Str",target);
    }
    xAuthMessages.send("String_Node_Str",player,target);
    xAuthLog.info(targetName + "String_Node_Str" + player.getName());
  }
 else   if (sender instanceof ConsoleCommandSender) {
    if (args.length < 2) {
      xAuthLog.info("String_Node_Str");
      return true;
    }
    String targetName=args[1];
    xAuthPlayer xPlayer=dataManager.getPlayer(targetName);
    if (!xPlayer.isRegistered()) {
      xAuthLog.info(targetName + "String_Node_Str");
      return true;
    }
    dataManager.deleteAccount(xPlayer);
    Player target=xPlayer.getPlayer();
    if (target != null) {
      plugin.createGuest(xPlayer);
      target.sendMessage("String_Node_Str");
    }
    xAuthLog.info(targetName + "String_Node_Str");
  }
  return true;
}

Fixed version (ground truth):
private boolean unregisterCommand(CommandSender sender,String[] args){
  if (sender instanceof Player) {
    Player player=(Player)sender;
    if (!xAuthPermissions.has(player,"String_Node_Str")) {
      xAuthMessages.send("String_Node_Str",player);
      return true;
    }
 else     if (args.length < 2) {
      xAuthMessages.send("String_Node_Str",player);
      return true;
    }
    String targetName=args[1];
    xAuthPlayer xPlayer=dataManager.getPlayer(targetName);
    if (!xPlayer.isRegistered()) {
      xAuthMessages.send("String_Node_Str",player,xPlayer.getPlayer());
      return true;
    }
    dataManager.deleteAccount(xPlayer);
    Player target=xPlayer.getPlayer();
    if (target != null) {
      if (xPlayer.mustRegister())       plugin.createGuest(xPlayer);
      xAuthMessages.send("String_Node_Str",target);
    }
    xAuthMessages.send("String_Node_Str",player,target);
    xAuthLog.info(targetName + "String_Node_Str" + player.getName());
  }
 else   if (sender instanceof ConsoleCommandSender) {
    if (args.length < 2) {
      xAuthLog.info("String_Node_Str");
      return true;
    }
    String targetName=args[1];
    xAuthPlayer xPlayer=dataManager.getPlayer(targetName);
    if (!xPlayer.isRegistered()) {
      xAuthLog.info(targetName + "String_Node_Str");
      return true;
    }
    dataManager.deleteAccount(xPlayer);
    Player target=xPlayer.getPlayer();
    if (target != null) {
      if (xPlayer.mustRegister())       plugin.createGuest(xPlayer);
      target.sendMessage("String_Node_Str");
    }
    xAuthLog.info(targetName + "String_Node_Str");
  }
  return true;
}