Error during install when old settings.php exists.

I can't use update.php from RC1 to RC2, so I try to reinstall again.
But old settings.php still exists for some settings.

After keyin database information, this error will show.

The website encountered an unexpected error. Please try again later.
Exception: invalid array index in drupal_rewrite_settings() (line 280 of core/includes/install.inc).
drupal_rewrite_settings(Array)
drupal_install_config_directories()
Drupal\Core\Installer\Form\SiteSettingsForm->submitForm(Array, Object)
call_user_func_array(Array, Array)
Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object)
Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object)
Drupal\Core\Form\FormBuilder->processForm('install_settings_form', Array, Object)
Drupal\Core\Form\FormBuilder->buildForm('Drupal\Core\Installer\Form\SiteSettingsForm', Object)
install_get_form('Drupal\Core\Installer\Form\SiteSettingsForm', Array)
install_run_task(Array, Array)
install_run_tasks(Array)
install_drupal(Object)