Re: [xwiki-users] $xwiki not always available?

I've seen a few of these, and it doesn't really have anything to do with the $xwiki reference (though perhaps the code should be changed to avoid that misleading message..). The original cause is an NPE originating out of Collections.sort, which is called by XWiki.sort: XWiki.sort: public List sort(List list) { Collections.sort(list); return list; } Collections.sort doesn't appear to check for null: public static <T extends Comparable<? super T>> void sort(List<T> list) { Object[] a = list.toArray(); Arrays.sort(a); Seems to me like your panel needs to make sure your list is non-null (not empty) before calling xwiki.sort

The recommended (from the velocity docs) way to check for non-null && not empty: #if( "$!allTags" != '') #set( $allTagsSorted = $xwiki.sort($allTags)) #end That should solve the problem.