Can't uninstall system application if set user.cachedir to a no-permission dir


Steps:
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on win_xp
1.Install jre b48 PIT from /net/dig-dug.east/bigtmp/deployment/1.6.0/pit/2005-08-11.14_37
2. Clean user and system cache ( if has setup system cache )
3.Setup system cache ( deployment.system.cachedir )
4. Using control panel, set the user cache to a location that the user has no permission to access
5. Launch a JNLP application using system cache (e.g javaws -system http://java.sun.com/products/javawebstart/apps/draw.jnlp)
The application launched successfully
6. Uninstall this application using javaws -system -uninstall
NullPointerException exception thrown
java.lang.NullPointerException
    at com.sun.deploy.cache.Cache.removeAllMuffins(Unknown Source)
    at com.sun.javaws.CacheUtil.remove(Unknown Source)
    at com.sun.javaws.Main.uninstallAll(Unknown Source)
    at com.sun.javaws.Main.uninstall(Unknown Source)
    at com.sun.javaws.Main.uninstallCache(Unknown Source)
    at com.sun.javaws.Main.continueInSecureThread(Unknown Source)
    at com.sun.javaws.Main$1.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)