Program: 35319
Project: 35319
Buggy source:
private void migrateDownloaders(OldConfig oldConfig){
  List<DownloaderConfig> downloaders=new ArrayList<>();
  for (  Downloader oldDownloader : oldConfig.getDownloaders()) {
    DownloaderConfig newDownloader=new DownloaderConfig();
    if (oldDownloader.getType().equals("String_Node_Str")) {
      newDownloader.setDownloaderType(DownloaderType.NZBGET);
      String url=(oldDownloader.isSsl() ? "String_Node_Str" : "String_Node_Str");
      if (!Strings.isNullOrEmpty(oldDownloader.getUsername()) && !Strings.isNullOrEmpty(oldDownloader.getPassword())) {
        url+=oldDownloader.getUsername() + "String_Node_Str" + oldDownloader.getPassword()+ "String_Node_Str";
      }
      url+=oldDownloader.getHost() + "String_Node_Str" + oldDownloader.getPort();
      newDownloader.setUrl(url);
    }
 else {
      newDownloader.setDownloaderType(DownloaderType.SABNZBD);
      newDownloader.setUrl(oldDownloader.getUrl());
    }
    newDownloader.setName(oldDownloader.getName());
    try {
      newDownloader.setNzbAddingType(NzbAddingType.valueOf((oldDownloader.getNzbAddingType().toUpperCase())));
    }
 catch (    IllegalArgumentException e) {
      newDownloader.setNzbAddingType(NzbAddingType.SEND_LINK);
    }
    newDownloader.setIconCssClass(oldDownloader.getIconCssClass());
    newDownloader.setDefaultCategory(oldDownloader.getDefaultCategory());
    newDownloader.setDownloadType(DownloadType.NZB);
    downloaders.add(newDownloader);
  }
  configProvider.getBaseConfig().setDownloaders(downloaders);
}

Fixed version (ground truth):
private List<String> migrateDownloaders(OldConfig oldConfig,BaseConfig newConfig){
  List<String> messages=new ArrayList<>();
  List<DownloaderConfig> downloaders=new ArrayList<>();
  for (  Downloader oldDownloader : oldConfig.getDownloaders()) {
    DownloaderConfig newDownloader=new DownloaderConfig();
    if (oldDownloader.getType().equals("String_Node_Str")) {
      newDownloader.setDownloaderType(DownloaderType.NZBGET);
      String url=(oldDownloader.isSsl() ? "String_Node_Str" : "String_Node_Str");
      if (!Strings.isNullOrEmpty(oldDownloader.getUsername()) && !Strings.isNullOrEmpty(oldDownloader.getPassword())) {
        url+=oldDownloader.getUsername() + "String_Node_Str" + oldDownloader.getPassword()+ "String_Node_Str";
      }
      url+=oldDownloader.getHost() + "String_Node_Str" + oldDownloader.getPort();
      newDownloader.setUrl(url);
    }
 else {
      newDownloader.setDownloaderType(DownloaderType.SABNZBD);
      newDownloader.setUrl(oldDownloader.getUrl());
    }
    newDownloader.setName(oldDownloader.getName());
    try {
      newDownloader.setNzbAddingType(NzbAddingType.valueOf((oldDownloader.getNzbAddingType().toUpperCase().replace("String_Node_Str","String_Node_Str").replace("String_Node_Str","String_Node_Str"))));
    }
 catch (    IllegalArgumentException e) {
      logAsWarningAndAdd(messages,"String_Node_Str" + oldDownloader.getName() + "String_Node_Str");
      newDownloader.setNzbAddingType(NzbAddingType.SEND_LINK);
    }
    if (oldDownloader.getNzbaccesstype().equals("String_Node_Str")) {
      newDownloader.setNzbAccessType(NzbAccessType.PROXY);
    }
 else {
      newDownloader.setNzbAccessType(NzbAccessType.REDIRECT);
    }
    newDownloader.setIconCssClass(oldDownloader.getIconCssClass());
    newDownloader.setDefaultCategory(oldDownloader.getDefaultCategory());
    newDownloader.setDownloadType(DownloadType.NZB);
    newDownloader.setEnabled(oldDownloader.isEnabled());
    downloaders.add(newDownloader);
  }
  newConfig.setDownloaders(downloaders);
  return messages;
}