Program: 1221
Project: 1221
Buggy source:
public UIDialogCreateNewWorld(String title,Vector2f size){
  super(title,size);
  _inputSeed=new UIInput(new Vector2f(256f,30f));
  _inputSeed.setVisible(true);
  _inputWorldTitle=new UIInput(new Vector2f(256f,30f));
  _inputWorldTitle.setVisible(true);
  _inputWorldTitleLabel=new UIText("String_Node_Str");
  _inputWorldTitleLabel.setColor(Color.darkGray);
  _inputWorldTitleLabel.getSize().y=16f;
  _inputWorldTitleLabel.setVisible(true);
  _inputSeedLabel=new UIText("String_Node_Str");
  _inputSeedLabel.setColor(Color.darkGray);
  _inputSeedLabel.getSize().y=16f;
  _inputSeedLabel.setVisible(true);
  _inputWorldTitleLabel.setPosition(new Vector2f(15f,32f));
  _inputWorldTitle.setPosition(new Vector2f(_inputWorldTitleLabel.getPosition().x,_inputWorldTitleLabel.getPosition().y + _inputWorldTitleLabel.getSize().y + 8f));
  _inputSeedLabel.setPosition(new Vector2f(_inputWorldTitle.getPosition().x,_inputWorldTitle.getPosition().y + _inputWorldTitle.getSize().y + 16f));
  _inputSeed.setPosition(new Vector2f(_inputSeedLabel.getPosition().x,_inputSeedLabel.getPosition().y + _inputSeedLabel.getSize().y + 8f));
  _okButton=new UIButton(new Vector2f(128f,32f));
  _okButton.getLabel().setText("String_Node_Str");
  _okButton.setPosition(new Vector2f(size.x / 2 - _okButton.getSize().x - 16f,size.y - _okButton.getSize().y));
  _okButton.setVisible(true);
  _okButton.addClickListener(new IClickListener(){
    public void clicked(    UIDisplayElement element){
      if (_inputSeed.getValue().length() > 0) {
        Config.getInstance().setDefaultSeed(_inputSeed.getValue());
      }
      if (_inputWorldTitle.getValue().length() > 0) {
        Config.getInstance().setWorldTitle(_inputWorldTitle.getValue());
      }
 else {
        Config.getInstance().setWorldTitle("String_Node_Str");
      }
      Terasology.getInstance().setGameState(Terasology.GAME_STATE.SINGLE_PLAYER);
    }
  }
);
  _cancelButton=new UIButton(new Vector2f(128f,32f));
  _cancelButton.setPosition(new Vector2f(_okButton.getPosition().x + _okButton.getSize().x + 16f,_okButton.getPosition().y));
  _cancelButton.getLabel().setText("String_Node_Str");
  _cancelButton.setVisible(true);
  _cancelButton.addClickListener(new IClickListener(){
    public void clicked(    UIDisplayElement element){
      setVisible(false);
    }
  }
);
  addDisplayElement(_okButton);
  addDisplayElement(_cancelButton);
  addDisplayElement(_inputSeed);
  addDisplayElement(_inputSeedLabel);
  addDisplayElement(_inputWorldTitleLabel);
  addDisplayElement(_inputWorldTitle);
}

Fixed version (ground truth):
public UIDialogCreateNewWorld(String title,Vector2f size){
  super(title,size);
  _inputSeed=new UIInput(new Vector2f(256f,30f));
  _inputSeed.setVisible(true);
  _inputWorldTitle=new UIInput(new Vector2f(256f,30f));
  _inputWorldTitle.setVisible(true);
  _inputWorldTitleLabel=new UIText("String_Node_Str");
  _inputWorldTitleLabel.setColor(Color.darkGray);
  _inputWorldTitleLabel.getSize().y=16f;
  _inputWorldTitleLabel.setVisible(true);
  _inputSeedLabel=new UIText("String_Node_Str");
  _inputSeedLabel.setColor(Color.darkGray);
  _inputSeedLabel.getSize().y=16f;
  _inputSeedLabel.setVisible(true);
  _inputWorldTitleLabel.setPosition(new Vector2f(15f,32f));
  _inputWorldTitle.setPosition(new Vector2f(_inputWorldTitleLabel.getPosition().x,_inputWorldTitleLabel.getPosition().y + _inputWorldTitleLabel.getSize().y + 8f));
  _inputSeedLabel.setPosition(new Vector2f(_inputWorldTitle.getPosition().x,_inputWorldTitle.getPosition().y + _inputWorldTitle.getSize().y + 16f));
  _inputSeed.setPosition(new Vector2f(_inputSeedLabel.getPosition().x,_inputSeedLabel.getPosition().y + _inputSeedLabel.getSize().y + 8f));
  _okButton=new UIButton(new Vector2f(128f,32f));
  _okButton.getLabel().setText("String_Node_Str");
  _okButton.setPosition(new Vector2f(size.x / 2 - _okButton.getSize().x - 16f,size.y - _okButton.getSize().y));
  _okButton.setVisible(true);
  _okButton.addClickListener(new IClickListener(){
    public void clicked(    UIDisplayElement element){
      if (_inputSeed.getValue().length() > 0) {
        Config.getInstance().setDefaultSeed(_inputSeed.getValue());
      }
      if (_inputWorldTitle.getValue().length() > 0) {
        Config.getInstance().setWorldTitle(_inputWorldTitle.getValue());
      }
 else {
        Config.getInstance().setWorldTitle("String_Node_Str");
      }
      Terasology.getInstance().setGameState(Terasology.GAME_STATE.SINGLE_PLAYER);
    }
  }
);
  _cancelButton=new UIButton(new Vector2f(128f,32f));
  _cancelButton.setPosition(new Vector2f(_okButton.getPosition().x + _okButton.getSize().x + 16f,_okButton.getPosition().y));
  _cancelButton.getLabel().setText("String_Node_Str");
  _cancelButton.setVisible(true);
  _cancelButton.addClickListener(new IClickListener(){
    public void clicked(    UIDisplayElement element){
      setVisible(false);
    }
  }
);
  addDisplayElement(_okButton,"String_Node_Str");
  addDisplayElement(_cancelButton,"String_Node_Str");
  addDisplayElement(_inputSeed,"String_Node_Str");
  addDisplayElement(_inputSeedLabel,"String_Node_Str");
  addDisplayElement(_inputWorldTitleLabel,"String_Node_Str");
  addDisplayElement(_inputWorldTitle,"String_Node_Str");
}