User switching doesn't work for usernames containing a space

If a username contains a space then that username will never show up in the "switch user" far right menu.

I've been able to figure a bit out about what's going on, but can't tell if it's a core, devel or a DAM bug.

Here's what I've figured out:

DAM calls devel_switch_user_list() via module_invoke('devel', 'switch_user_list') in admin_menu_admin_menu() to get the list of users who can be switched to.

Note that devel_switch_user_list() uses l() to generate the relevant link in the form "devel/switch/[username]". If username contains a space then the link generated is eg. "devel/switch/john%20doe" (as it should).

Later, _menu_link_translate() will return false because of this code (line 644 in 6.5):

// Note - skip callbacks without real values for their arguments.
if (strpos($item['href'], '%') !== FALSE) {
  $item['access'] = FALSE;
  return FALSE;
}

Because of this the DAM menu item for switching to "john doe" never gets added. Let me know if more info is needed.