Error in updating a CPT

When seeking help with this issue, you may be asked for some of the following information:
WordPress version 6.8.1
Active theme: Newspaper Child theme (version 9.0c)
Current plugin: tagDiv Opt-In Builder (version 1.7.1 | built on 29.04.2025 10:50)
PHP version 8.3.6

Error Details
=============
An error of type E_ERROR was caused in line 3276 of the file /wp-content/plugins/td-subscription/includes/td_subscription.php. Error message: Uncaught TypeError: array_key_exists(): Argument #2 ($array) must be of type array, null given in /wp-content/plugins/td-subscription/includes/td_subscription.php:3276
Stack trace:
#0 /wp-includes/class-wp-hook.php(324): td_subscription::td_post_theme_settings_mb_save_filter()
#1 /wp-includes/plugin.php(205): WP_Hook->apply_filters()
#2 /wp-content/plugins/td-composer/legacy/common/wp_booster/wp-admin/external/wpalchemy/MetaBox.php(880): apply_filters()
#3 /wp-content/plugins/td-composer/legacy/common/wp_booster/wp-admin/external/wpalchemy/MetaBox.php(2081): WPAlchemy_MetaBox->apply_filters()
#4 /wp-includes/class-wp-hook.php(326): WPAlchemy_MetaBox->_save()
#5 /wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#6 /wp-includes/plugin.php(517): WP_Hook->do_action()
#7 /wp-includes/post.php(5110): do_action()
#8 /wp-includes/post.php(5212): wp_insert_post()
#9 /wp-admin/includes/post.php(453): wp_update_post()
#10 /wp-admin/post.php(227): edit_post()
#11 {main}
thrown

A function is trying to use array_key_exists() on a variable that is null instead of an array.

**How to fix:**
– The plugin author should ensure that the second argument to array_key_exists() is always an array.
– As a quick fix, you can wrap the call with an is_array() check.

**Example fix:**
`php
if (is_array($array) && array_key_exists($key, $array)) {
// ...existing code...
}
`