Wordpress array null - php

Question

I have a checkout system, within my Wordpress that shows me the following message:
Notice: Undefined index: answers in
/srv/www/vhosts/wordpress/wp-content/themes/../checkout/fragment-header.php
on line 3
Notice: Trying to access array offset on value of type null in
/srv/www/vhosts/wordpress/wp-content/themes/../checkout/fragment-header.php
on line 3
The php code of that file is the following:
<?php
$valorAccesorio = $args['quote']['answers']['vehicleGncValue'] ?? '0';
$cuotaMensual = $args['quote']['answers']['planPremioMensual'] +
(isset($args['quote']['answers']['apPremioMensual']) ? $args['quote']['answers']['apPremioMensual'] : 0);
?>
<header id="header">
<div class="wrap menu-wrap">
<?php
$class = (theme_get_custom_logo()) ? 'image' : 'text';
echo '<h1 class="site-title ' . $class . '">';
echo '<a href="' . esc_url(home_url('/')) . '" rel="home">';
if (theme_get_custom_logo()) echo '<img src="' . theme_get_custom_logo() . '" class="site-logo" alt="' . htmlspecialchars(get_bloginfo('name')) . '" />';
echo '<strong>' . get_bloginfo('name') . '</strong>';
echo '</a>';
echo '</h1>';
?>
<div class="right-section">
<?php if ($args['quote']['product'] == 'seguro-de-motos' || $args['quote']['product'] == 'seguro-de-autos-y-pick-ups') : ?>
<h1>
Estás contratando un plan
<span><?php echo $args['quote']['answers']['planCobertura'] ?></span>,
para tu
<span>
<?php echo $args['quote']['answers']['vehicleBrand'] ?>
<?php if (isset($args['quote']['answers']['vehicleModel'])) {
echo $args['quote']['answers']['vehicleModel'];
} else {
echo $args['quote']['answers']['vehicleVersion'];
} ?>
<?php echo $args['quote']['answers']['vehicleYear'] ?>
</span>
</h1>
<p>
Suma asegurada: $<?php echo number_format(($args['quote']['answers']['vehicleValue'] + $valorAccesorio), 2, ',', '.') ?>
|
Cuota mensual: $<?php echo number_format(($cuotaMensual), 2, ',', '.') ?>
</p>
<?php endif; ?>
</div>
From what I understand I am generating an array with null value, but I do not understand how to generate it by another way
Some help? Thanks!