NullPointerExcept when searching an existing attachment with no right to view

From Wesley Huang:

In my xwiki.log file, I see many NullPointExcept. One of them is related
to the lucene search on an existing attachment when the user has no
right to view it. For example, I attached a sunset.jpg in a privileged
space, after logged out, and do a search with keyword "sunset.jpg", then
NullPointException throws in the xwiki logs. While there is no error
shows on the lucene result page, it is fairly annoying to see non-sense
errors in the logs.

Does anyone have an idea to fix it?

2010-07-28 12:53:33,095
[<Site>/xwiki/bin/view/Main/Search?text=sunset.jpg&space=]
[<Site>/xwiki/bin/view/Main/Search?text=sunset.jpg&space=] ERROR
lucene.SearchResults - Error getting search result
java.lang.NullPointerException
at
com.xpn.xwiki.plugin.lucene.SearchResult.<init>(SearchResult.java:99)
at
com.xpn.xwiki.plugin.lucene.SearchResults.getRelevantResults(SearchResults.java:72)
at
com.xpn.xwiki.plugin.lucene.SearchResults.getHitcount(SearchResults.java:229)
at sun.reflect.GeneratedMethodAccessor477.invoke(Unknown Source)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
.......