On line 268 of webform_conditional.module foreach ($javascript['settings']['data'] as $delta => $settings) { causes a PHP 'Undifined index: settings' warning if no javascript has been previously added with drupal_add_js. (I am using this in the install profile, that is why no js has been added yet).

I was able to fix this by adding a check to the existence of $javascript['settings']['data'] in webform_conditional_add_js:

function webform_conditional_add_js(&$form, $form_state) {
  // If the form is being rebuilt we need to reset the previous settings,
  // otherwise array_merge_recursive() will turn string values into arrays.
  $javascript = &drupal_static('drupal_add_js', array());
  if (isset($javascript['settings']['data'])) {
      foreach ($javascript['settings']['data'] as $delta => $settings) {
        if (key($settings) == 'webform_conditional') {
          unset($javascript['settings']['data'][$delta]);
          break;
        }
      }
  }
  drupal_add_js($form['#webform_conditional_js'], array('type' => "setting", 'scope' => JS_DEFAULT));
  drupal_add_js(drupal_get_path('module', 'webform_conditional') . '/webform_conditional.js');
  return $form;
}