Undefined index: maintenance in .... (after Facebook Bussines Extension Upload)

Hi guys! I ve just uploaded the Facebook Bussiness Extension, as well as the Facebook pixel. Works everything fine, however I ve got this notice:

Opencart 2.1.0.1.

Notice: Undefined index: maintenance in /web/lolasart/lolasart.hu/system/storage/modification/catalog/controller/common/header.php on line 39

The code (the line 39 is highlited)
<?php
class ControllerCommonHeader extends Controller {
public function index() {

$data['facebook_page_id_FAE'] =
$this->config->get(FacebookCommonUtils::FACEBOOK_PAGE_ID);
$data['facebook_jssdk_version_FAE'] =
$this->config->get(FacebookCommonUtils::FACEBOOK_JSSDK_VER);
$data['facebook_messenger_enabled_FAE'] =
$this->config->get(FacebookCommonUtils::FACEBOOK_MESSENGER);
// default locale to en_US if setting is not available
$customization_locale = $this->config->get(
FacebookCommonUtils::FACEBOOK_CUSTOMIZATION_LOCALE);
$data['facebook_customization_locale_FAE'] =
($customization_locale)
? $customization_locale
: 'en_US';


$data['facebook_pixel_id_FAE'] =
$this->fbevents['facebook_pixel_id_FAE'];
$data['facebook_pixel_pii_FAE'] =
$this->fbevents['facebook_pixel_pii_FAE'];
$data['facebook_pixel_params_FAE'] =
$this->fbevents['facebook_pixel_params_FAE'];
$data['facebook_pixel_params_FAE'] =
$this->fbevents['facebook_pixel_params_FAE'];
$data['facebook_pixel_event_params_FAE'] =
$this->fbevents['facebook_pixel_event_params_FAE'];
$data['facebook_enable_cookie_bar'] =
$this->fbevents['facebook_enable_cookie_bar'];

// remove away the facebook_pixel_event_params_FAE in session data
// to avoid duplicate firing after the 1st fire
unset($this->session->data['facebook_pixel_event_params_FAE']);

// pull in the cookie bar settings from the language bar

if (($data['maintenance']==0)) {
$data['informations'] = array();
foreach ($this->model_catalog_information->getInformations() as $result) {
if ($result['bottom']) {
$data['informations'][] = array(
'title' => $result['title'],
'href' => $this->url->link('information/information', 'information_id=' . $result['information_id'])
);
}
}
}

Can anyone help me how can I fix this?
Thank you in advance!

Contact the extension developer to resolve this issue.

The extension provided by Facebook is not performing well. To avoid such problem you can contact any other vendor so, as to run your ads bug free. In case of other vendor you can get quick support with out interruption any of your on going campaigns.