Jump menu grouping doesn't work with a sorted view

Adding a sort field on a view configured with the jump menu display, with grouping enabled, causes options within the select menu to appear outside of their group. Consider the example of a jump menu configured to display uid and usernames grouped by roles :

- Editors
-- 1: mike
-- 2: jim
- Authors
-- 3: bob

With no sorting active on the view, the users appear in a default order of uid (the order returned by the SQL query, I suppose), and they also appear under the correct role grouping. When one adds sorting by username on the view, the jump menu appears as such:

- Editors
-- 3: bob
-- 2: jim
- Authors
-- 1: mike

This is wrong, because "bob" is an "Author" and "mike" is an "Editor" : the select options are sorted regardless of grouping. The expected output is this :

- Editors
-- 2: jim
-- 1: mike
- Authors
-- 3: bob

I tracked this down to the foreach structures in views_plugin_style_jump_menu.inc that transform the result set into options for the select menu. Options are added to the select menu according to the result set order, regardless of groupings.

Here's a rough patch against 6.x-2.x-dev that fixes the problem.