NullPointerException using WindowsProgressBarUI with unknown XPStyle pro

FULL PRODUCT VERSION :
java version "1.5.0_05"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_05-b05)
Java HotSpot(TM) Client VM (build 1.5.0_05-b05, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Windows XP Home SP2

EXTRA RELEVANT SYSTEM CONFIGURATION :
Our customer uses some (unknown to me) Windows XP-Style/Theme!

A DESCRIPTION OF THE PROBLEM :
Within our application (running on our customers machines) we get the following exception:

java.lang.NullPointerException
at java.awt.Dimension.<init>(Dimension.java:91)
at javax.swing.plaf.basic.BasicProgressBarUI.getPreferredSize(BasicProgressBarUI.java:757)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1582)
at java.awt.GridBagLayout.GetLayoutInfo(GridBagLayout.java:911)
at java.awt.GridBagLayout.getLayoutInfo(GridBagLayout.java:816)
at java.awt.GridBagLayout.ArrangeGrid(GridBagLayout.java:1412)
at java.awt.GridBagLayout.arrangeGrid(GridBagLayout.java:1372)
at java.awt.GridBagLayout.layoutContainer(GridBagLayout.java:712)
at java.awt.Container.layout(Container.java:1401)
at java.awt.Container.doLayout(Container.java:1390)
at java.awt.Container.validateTree(Container.java:1473)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validate(Container.java:1448)
at java.awt.Window.show(Window.java:507)
at java.awt.Component.show(Component.java:1300)
at java.awt.Component.setVisible(Component.java:1253)


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Since the problem only arises on our customers side where we do only have a very limited access, I think the cause of the problem is as follows.
- Windows Look&Feel (com.sun.java.swing.plaf.windows.WindowsLookAndFeel)

- XPStyle returns ´null´:
   /** Get a named <code>Dimension</code> value from the current style
     *
     * @param key a <code>String</code>
     * @return a <code>Dimension</code> or null if key is not found
     * in the current style
     */
    synchronized Dimension getDimension(String key) {
Dimension d = (Dimension)map.get("Dimension "+key);
// assume d==null
if (d == null) {
String str = getString(key);
// assume str==null, skip if
if (str != null) {
StringTokenizer tok = new StringTokenizer(str, " \t,");
d = new Dimension(parseInt(tok.nextToken(), 0),
parseInt(tok.nextToken(), 0));
map.put("Dimension "+key, d);
}
}
// return null
return d;
    }


- then WindowsProgressBarUI returns ´null´
    protected Dimension getPreferredInnerHorizontal() {
XPStyle xp = XPStyle.getXP();
if (xp != null) {
// return null
return xp.getDimension("progress.bar.normalsize");
} else {
return super.getPreferredInnerHorizontal();
}
    }

- then BasicProgressBarUI feeds a null Dimension
    public Dimension getPreferredSize(JComponent c) {
Dimension size;
Insets border = progressBar.getInsets();
FontMetrics fontSizer = progressBar.getFontMetrics(
          progressBar.getFont());

if (progressBar.getOrientation() == JProgressBar.HORIZONTAL) {
// new Dimension( null ) !!
size = new Dimension(getPreferredInnerHorizontal());
...
into the new Dimension(..) which actually fails.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Use some default values, or have any fallback strategy, however no NPE

ERROR MESSAGES/STACK TRACES THAT OCCUR :

java.lang.NullPointerException
at java.awt.Dimension.<init>(Dimension.java:91)
at javax.swing.plaf.basic.BasicProgressBarUI.getPreferredSize(BasicProgressBarUI.java:757)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1582)
at java.awt.GridBagLayout.GetLayoutInfo(GridBagLayout.java:911)
at java.awt.GridBagLayout.getLayoutInfo(GridBagLayout.java:816)
at java.awt.GridBagLayout.ArrangeGrid(GridBagLayout.java:1412)
at java.awt.GridBagLayout.arrangeGrid(GridBagLayout.java:1372)
at java.awt.GridBagLayout.layoutContainer(GridBagLayout.java:712)
at java.awt.Container.layout(Container.java:1401)
at java.awt.Container.doLayout(Container.java:1390)
at java.awt.Container.validateTree(Container.java:1473)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validate(Container.java:1448)
at java.awt.Window.show(Window.java:507)
at java.awt.Component.show(Component.java:1300)
at java.awt.Component.setVisible(Component.java:1253)


REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
switch XP Style back to default