Empty facet links don't work for language facets

Adding an empty facet to the languages block doesn't work:

From apachesolr.module function apachesolr_facet_block():

      if ($facet == '_empty_') {
         $exclude = TRUE;
         $facet = '[* TO *]';
         $facet_text = theme('placeholder', t('Missing this field'));
         $options['html'] = TRUE;
         // Put this just below any active facets.
         // '-' sorts before all numbers, but after '*'.
         $sortpre = '-';
       }

This will generate a URL with: ?filters=-language%3A[* TO *]