warnings on block configuration

When accessing Forward block configuration page, warnings for form.inc at line 15xx line are displayed (_form_set_class function).
This is because of the line 660 in the forward.module. '#attribute' must be an array (in the module it can be ommited).

Original code:

    $form['forward_block_type'] = array(
        '#type' => 'radios',
        '#title' => t('Block Type'),
        '#default_value' => variable_get('forward_block_type', " "),
        '#options' => $block_options,
        '#description' => t('Choose the block type'),
        '#required' => null,
        '#attributes' => true,
    );

Resulting code:

    $form['forward_block_type'] = array(
        '#type' => 'radios',
        '#title' => t('Block Type'),
        '#default_value' => variable_get('forward_block_type', " "),
        '#options' => $block_options,
        '#description' => t('Choose the block type'),
    );