[bp/r53369][FIX] groupChoice: Fields param to wikiplugin_tracker is expected to be an array (since 12.2 or 12.3) so user tracker fields were not appearing. Thanks Xavi, should address wish5501. Thanks jonnyb

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/13.x@53370 b456876b-0849-0410-b77d-98878d47e9d5