Vocabulary set to None selected disables Selection options

When editing an existing profile field which has the Vocabulary set to 'None selected' the Selection options are disabled and also empty, I believe it has something to do with:

<?php
Drupal.profile_taxonomy.exportTerms = function(widget, context) {
  var vid = $('#edit-vocabulary', context).val();
  if (vid != 0) {
    ...
  }
  else { // no vocabulary selection, fall back into standard mode
    $('#edit-options').removeAttr('disabled');
    $('#edit-options').val(''); 
    $('#edit-parent-term').children(":not(option:first)").remove().end();
  }
};
?>

This is in profile_taxonomy.js but I'm not an expert when it comes to JavaScript and jQuery so I'm not sure what the changes should be