NullPointerException em JFrame [RESOLVIDO]

Exception in thread “AWT-EventQueue-0” java.lang.NullPointerException

at java.awt.Window.initGC(Window.java:464)

at java.awt.Window.init(Window.java:484)

at java.awt.Window.(Window.java:533)

at java.awt.Frame.(Frame.java:418)

at java.awt.Frame.(Frame.java:383)

at javax.swing.JFrame.(JFrame.java:180)

at br.ufpa.linc.view.principal.Principal.(Principal.java:27)

at br.ufpa.linc.view.principal.Principal.getPrincipal(Principal.java:280)

at br.ufpa.linc.view.principal.Principal$6.run(Principal.java:295)

at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)

at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:705)

at java.awt.EventQueue.access$000(EventQueue.java:101)

at java.awt.EventQueue$3.run(EventQueue.java:666)

at java.awt.EventQueue$3.run(EventQueue.java:664)

at java.security.AccessController.doPrivileged(Native Method)

at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)

at java.awt.EventQueue.dispatchEvent(EventQueue.java:675)

at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:240)

at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:157)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:146)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:142)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:134)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

public class NewJFrame extends javax.swing.JFrame {

    public NewJFrame() {
        super("Teste");
        initComponents();
    }
                         
    private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 300, Short.MAX_VALUE)
        );

        pack();
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new NewJFrame().setVisible(true);
            }
        });
    }          
}