When using the Look and Feel library does a spacing appear, is this an error as I can correct it?

The problem I have is that when I import a look and Feel library I get it as a spacing below, and I probe turning off the setResizable but it did not solve the problem, then I thought it was the image and it is not, it seems as if was it a scroll in my opinion, then some way to make it disappear?

I hope you can help me thanks

This is the Look And Feel library that I use:

public static void main(String[] args) {
    try {

        UIManager.setLookAndFeel("de.javasoft.plaf.synthetica.SyntheticaClassyLookAndFeel");
        MantenimientoEmpleado dialog = new MantenimientoEmpleado();

        dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
        dialog.setVisible(true);
    } catch (Exception e) {
        e.printStackTrace();
    }
}