[Closed] [Visit Pula] Your Site is Experiencing a Technical Issue

Background of the issue:
I am trying to resolve a technical issue on my site. An error of type E_ERROR was caused in line 169 of the file /home/customer/www/visitpula.hr/public_html/stay/wp-content/plugins/wpml-sticky-links/classes/custom-fields.php. The error message is: Uncaught TypeError: array_key_exists(): Argument #2 ($array) must be of type array, bool given in /home/customer/www/visitpula.hr/public_html/stay/wp-content/plugins/wpml-sticky-links/classes/custom-fields.php:169. Link to a page where the issue can be seen: hidden link

Symptoms:
The site is experiencing a technical issue with an error message indicating a TypeError in the WPML Sticky Links plugin.

Error Details
=============
An error of type E_ERROR was caused in line 169 of the file /home/customer/www/visitpula.hr/public_html/stay/wp-content/plugins/wpml-sticky-links/classes/custom-fields.php. Error message: Uncaught TypeError: array_key_exists(): Argument #2 ($array) must be of type array, bool given in /home/customer/www/visitpula.hr/public_html/stay/wp-content/plugins/wpml-sticky-links/classes/custom-fields.php:169
Stack trace:
#0 /home/customer/www/visitpula.hr/public_html/stay/wp-content/plugins/wpml-sticky-links/classes/custom-fields.php(169): array_key_exists('custom_fields_c...', false)
#1 /home/customer/www/visitpula.hr/public_html/stay/wp-content/plugins/wpml-sticky-links/classes/custom-fields.php(83): WPMLSLCustomFields->getSettings()
#2 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/class-wp-hook.php(324): WPMLSLCustomFields->convertUrlsInCustomField('9970', 35720, '_edit_lock', '1743447094:2')
#3 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)
#4 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#5 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/meta.php(336): do_action('updated_post_me...', '9970', 35720, '_edit_lock', '1743447094:2')
#6 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/post.php(2648): update_metadata('post', 35720, '_edit_lock', '1743447094:2', '')
#7 /home/customer/www/visitpula.hr/public_html/stay/wp-admin/includes/post.php(1762): update_post_meta(35720, '_edit_lock', '1743447094:2')
#8 /home/customer/www/visitpula.hr/public_html/stay/wp-content/plugins/elementor/core/editor/editor.php(291): wp_set_post_lock(Object(WP_Post))
#9 /home/customer/www/visitpula.hr/public_html/stay/wp-content/plugins/elementor/includes/heartbeat.php(40): ElementorCoreEditorEditor->lock_post('35720')
#10 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/class-wp-hook.php(326): ElementorHeartbeat->heartbeat_received(Array, Array)
#11 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/plugin.php(205): WP_Hook->apply_filters(Array, Array)
#12 /home/customer/www/visitpula.hr/public_html/stay/wp-admin/includes/ajax-actions.php(3503): apply_filters('heartbeat_recei...', Array, Array, 'front')
#13 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/class-wp-hook.php(324): wp_ajax_heartbeat('')
#14 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array)
#15 /home/customer/www/visitpula.hr/public_html/stay/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#16 /home/customer/www/visitpula.hr/public_html/stay/wp-admin/admin-ajax.php(192): do_action('wp_ajax_heartbe...')
#17 {main}
thrown

Questions:
What is causing the TypeError in the WPML Sticky Links plugin?
How can I fix the error related to array_key_exists in the custom-fields.php file?