Validation handler for shortcut_set_add_form().
function shortcut_set_add_form_validate($form, &$form_state) {
// Check to prevent a duplicate title.
if (shortcut_set_title_exists($form_state['values']['new'])) {
form_set_error('new', t('The shortcut set %name already exists. Choose another name.', array(
'%name' => $form_state['values']['new'],
)));
}
}