Program: 159143
Project: 159143
Buggy source:
private void startGame(UUID choosingPlayerId) throws GameException {
  try {
    match.startGame();
    table.initGame();
    GameManager.getInstance().createGameSession(match.getGame(),userPlayerMap,table.getId(),choosingPlayerId);
    String creator=null;
    StringBuilder opponent=new StringBuilder();
    for (    Entry<UUID,UUID> entry : userPlayerMap.entrySet()) {
      if (!match.getPlayer(entry.getValue()).hasQuit()) {
        User user=UserManager.getInstance().getUser(entry.getKey());
        if (user != null) {
          if (!user.isConnected()) {
            user.removeConstructing(match.getPlayer(entry.getValue()).getPlayer().getId());
            GameManager.getInstance().joinGame(match.getGame().getId(),user.getId());
            logger.debug("String_Node_Str" + user.getName() + "String_Node_Str"+ match.getId());
          }
          user.gameStarted(match.getGame().getId(),entry.getValue());
          if (creator == null) {
            creator=user.getName();
          }
 else {
            if (opponent.length() > 0) {
              opponent.append("String_Node_Str");
            }
            opponent.append(user.getName());
          }
        }
 else {
          logger.error("String_Node_Str" + entry.getKey() + "String_Node_Str"+ entry.getValue());
          MatchPlayer matchPlayer=match.getPlayer(entry.getValue());
          if (matchPlayer != null && !matchPlayer.hasQuit()) {
            matchPlayer.setQuit(true);
          }
        }
      }
 else {
        throw new MageException("String_Node_Str" + entry.getKey());
      }
    }
    for (    MatchPlayer mPlayer : match.getPlayers()) {
      if (!mPlayer.getPlayer().isHuman()) {
        if (opponent.length() > 0) {
          opponent.append("String_Node_Str");
        }
        opponent.append(mPlayer.getName());
      }
    }
    ServerMessagesUtil.getInstance().incGamesStarted();
    logger.info("String_Node_Str" + match.getName() + "String_Node_Str"+ creator+ "String_Node_Str"+ opponent.toString());
    logger.debug("String_Node_Str" + match.getId() + "String_Node_Str"+ match.getName()+ "String_Node_Str");
    if (match.getGame() != null) {
      logger.debug("String_Node_Str" + match.getGame().getId());
      logger.debug("String_Node_Str" + GameManager.getInstance().getChatId(match.getGame().getId()));
    }
 else {
      logger.debug("String_Node_Str");
    }
    LogServiceImpl.instance.log(LogKeys.KEY_GAME_STARTED,String.valueOf(userPlayerMap.size()),creator,opponent.toString());
  }
 catch (  Exception ex) {
    logger.fatal("String_Node_Str",ex);
    if (table != null) {
      TableManager.getInstance().removeTable(table.getId());
    }
    if (match != null) {
      Game game=match.getGame();
      if (game != null) {
        GameManager.getInstance().removeGame(game.getId());
      }
    }
  }
}

Fixed version (ground truth):
private void startGame(UUID choosingPlayerId) throws GameException {
  try {
    match.startGame();
    table.initGame();
    GameManager.getInstance().createGameSession(match.getGame(),userPlayerMap,table.getId(),choosingPlayerId);
    String creator=null;
    StringBuilder opponent=new StringBuilder();
    int activePlayers=0;
    for (    Entry<UUID,UUID> entry : userPlayerMap.entrySet()) {
      if (!match.getPlayer(entry.getValue()).hasQuit()) {
        activePlayers++;
        User user=UserManager.getInstance().getUser(entry.getKey());
        if (user != null) {
          if (!user.isConnected()) {
            user.removeConstructing(match.getPlayer(entry.getValue()).getPlayer().getId());
            GameManager.getInstance().joinGame(match.getGame().getId(),user.getId());
            logger.debug("String_Node_Str" + user.getName() + "String_Node_Str"+ match.getId());
          }
          user.gameStarted(match.getGame().getId(),entry.getValue());
          if (creator == null) {
            creator=user.getName();
          }
 else {
            if (opponent.length() > 0) {
              opponent.append("String_Node_Str");
            }
            opponent.append(user.getName());
          }
        }
 else {
          logger.error("String_Node_Str" + entry.getKey() + "String_Node_Str"+ entry.getValue());
          MatchPlayer matchPlayer=match.getPlayer(entry.getValue());
          if (matchPlayer != null && !matchPlayer.hasQuit()) {
            matchPlayer.setQuit(true);
          }
        }
      }
    }
    if (activePlayers < 2) {
      throw new MageException("String_Node_Str" + activePlayers);
    }
    for (    MatchPlayer mPlayer : match.getPlayers()) {
      if (!mPlayer.getPlayer().isHuman()) {
        if (opponent.length() > 0) {
          opponent.append("String_Node_Str");
        }
        opponent.append(mPlayer.getName());
      }
    }
    ServerMessagesUtil.getInstance().incGamesStarted();
    logger.info("String_Node_Str" + match.getName() + "String_Node_Str"+ creator+ "String_Node_Str"+ opponent.toString());
    logger.debug("String_Node_Str" + match.getId() + "String_Node_Str"+ match.getName()+ "String_Node_Str");
    if (match.getGame() != null) {
      logger.debug("String_Node_Str" + match.getGame().getId());
      logger.debug("String_Node_Str" + GameManager.getInstance().getChatId(match.getGame().getId()));
    }
 else {
      logger.debug("String_Node_Str");
    }
    LogServiceImpl.instance.log(LogKeys.KEY_GAME_STARTED,String.valueOf(userPlayerMap.size()),creator,opponent.toString());
  }
 catch (  Exception ex) {
    logger.fatal("String_Node_Str",ex);
    if (table != null) {
      TableManager.getInstance().removeTable(table.getId());
    }
    if (match != null) {
      Game game=match.getGame();
      if (game != null) {
        GameManager.getInstance().removeGame(game.getId());
      }
    }
  }
}