menu item titles w/ spaces result in output of invalid markup

Drupal allows spaces when setting title for menu items; the YUI Menu module's way of generating id values for the div holding each drop-down menu doesn't seem to account for this at present and results in id values with spaces, which isn't allowed under XHTML standards:

line 236 in yuimenu.module:

$output .= '<div id="'. rep_char($menu['visible'][$mid]['title']).'" class="yuimenu">

This is my admittedly janky way of fixing this:

$output .= '<div id="'.str_replace (" ", "", rep_char($menu['visible'][$mid]['title'])).'" class="yuimenu">

No doubt there's a cleaner way which can account for these and other special chars allowed by Drupal but not allowed by W3C standards. Apologies as I am not a dev by trade! :)