Reverts unwanted change (#24769).

git-svn-id: http://svn.redmine.org/redmine/trunk@16318 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/redmine/field_format.rb

@@ -793,8 +793,6 @@ module Redmine
             end
           end
           scope.sorted
-        elsif object.nil?
-          Principal.member_of(Project.visible.to_a).sorted.select {|p| p.is_a?(User)}
         else
           []
         end