ListGrid.preloadImages () causes NPE?

[shortpasta]

Using:
GWT 2.5.0
SmartClient Version: v8.3p_2012-11-23/LGPL Development Only (built 2012-11-23)
FF 6.0.2

I am looking into preloading images, and ran across ListGrid.preloadImages ().
But when I call it at application bootup, I get this:

00:00:36.650 [ERROR] <E> <Controller> <>java.lang.NullPointerException: null
 at com.smartgwt.client.util.FileLoader.cacheImg(FileLoader.java:67)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
 at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
 at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
 at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:338)
 at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
 at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
 at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:571)

Which is on line #2 of this (baseImageURL appears to be null):

    /**
     * Cache a list of images
     *
     * @param skinImgDir   the skinImgDir
     * @param baseImageURL the base urls
     */
    public static void cacheImg(String skinImgDir, String baseImageURL) {
        String skinDir = getSkinDir();
        baseImageURL = baseImageURL.replace("[SKINIMG]", skinDir + "images/");
        baseImageURL = baseImageURL.replace("[SKIN]", skinDir + skinImgDir);
        Image.prefetch(baseImageURL);
    }

So I looked at the Showcase
http://code.google.com/p/smartgwt/so...ase.java?r=873

And did this:

EdgedCanvas.preloadImages ();
Scrollbar.preloadImages ();
TabSet.preloadImages ();
Window.preloadImages ();
IButton.preloadImages ();
ListGrid.preloadImages ();

Out of all these classes, ListGrid is the only one that fails with the same exception.

Any advice?