NullPointerException while uninstalling appln from system cache and the user cache is configured to the directory which is not writable

Tested build : 6U10 b27 PIT
Tested OS : windows

-> Install jre
-> Clear user cache and system cache
-> Enable System cache
-> Launch Java Control Panel
-> Click "Settings..."
-> Enter a path for user cache location, which does not have write permission
-> Save the changes and close JCP
-> Launch a JNLP Application using system cache
(javaws -system http://java.sun.com/products/javawebstart/apps/notepad.jnlp)
notepad appln launched successfully
-> try to uninstall notepad appln from system cache using javaws -system -uninstall
or
javaws -system -uninstall http://java.sun.com/products/javawebstart/apps/notepad.jnlp

Unable to uninstall application dialog came up. clicking Details button show the NullPointerException :

Unexpected exception: java.lang.NullPointerException
java.lang.NullPointerException
        at com.sun.deploy.cache.Cache.removeAllCacheEntries(Unknown Source)
        at com.sun.javaws.CacheUtil.removeEntries(Unknown Source)
        at com.sun.javaws.CacheUtil.remove(Unknown Source)
        at com.sun.javaws.CacheUtil.remove(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)

Image file attached