Batch ignores #redirect due to checking undefined $batch instead of $_batch

bug:

function _batch_finished() {
// [...] here $batch is always NULL
    // Let drupal_redirect_form handle redirection logic.
    $form = isset($batch['form']) ? $batch['form'] : array();
    if (empty($_batch['form_state']['rebuild']) && empty($_batch['form_state']['storage'])) {
      drupal_redirect_form($form, $redirect);
    }

Fix:

function _batch_finished() {
// [...]
    // Let drupal_redirect_form handle redirection logic.
    $form = isset($_batch['form']) ? $_batch['form'] : array();
    if (empty($_batch['form_state']['rebuild']) && empty($_batch['form_state']['storage'])) {
      drupal_redirect_form($form, $redirect);
    }

As can be seen, since $batch is always empty, it sends an empty array to drupal_redirect_form instead of the form array, o $form['#redirect'] doesn't work.