Uncaught TypeError: Cannot access offset of type string on string: flexible-content - prepare_field_for_import()

[aptoptout]

Describe the bug
Getting a PHP Fatal error after uploading ACF Pro on a fresh Wordpress 6.7.1 + PHP8.2 install.

PHP Fatal error:
Uncaught TypeError: Cannot access offset of type string on string in /var/www/html/wp-content/plugins/advanced-custom-fields-pro/pro/fields/class-acf-field-flexible-content.php:1467

Stack trace:
#0 /var/www/html/wp-includes/class-wp-hook.php(324): acf_field_flexible_content->prepare_field_for_import(Array)
#1 /var/www/html/wp-includes/plugin.php(256): WP_Hook->apply_filters(Array, Array)
#2 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/acf-hook-functions.php(109): apply_filters_ref_array('acf/prepare_fie...', Array)
#3 /var/www/html/wp-includes/class-wp-hook.php(324): _acf_apply_hook_variations(Array)
#4 /var/www/html/wp-includes/plugin.php(205): WP_Hook->apply_filters(Array, Array)
#5 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/acf-field-functions.php(1626): apply_filters('acf/prepare_fie...', Array)
#6 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/acf-field-functions.php(1578): acf_prepare_field_for_import(Array)
#7 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/local-fields.php(404): acf_prepare_fields_for_import(Array)
#8 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/includes/local-fields.php(729): acf_add_local_fields(Array)
#9 /var/www/html/wp-includes/class-wp-hook.php(324): _acf_do_prepare_local_fields(5)
#10 /var/www/html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array)
#11 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#12 /var/www/html/wp-content/plugins/advanced-custom-fields-pro/acf.php(378): do_action('acf/include_fie...', 5)
#13 /var/www/html/wp-includes/class-wp-hook.php(324): ACF->init('')
#14 /var/www/html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)
#15 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#16 /var/www/html/wp-settings.php(704): do_action('init')
#17 /var/www/html/wp-config.php(139): require_once('/var/www/html/w...')
#18 /var/www/html/wp-load.php(50): require_once('/var/www/html/w...')
#19 /var/www/html/wp-admin/admin.php(34): require_once('/var/www/html/w...')
#20 /var/www/html/wp-admin/plugins.php(10): require_once('/var/www/html/w...')
#21 {main}
  thrown in /var/www/html/wp-content/plugins/advanced-custom-fields-pro/pro/fields/class-acf-field-flexible-content.php on line 1467, referer: http://localhost:8080/wp-admin/update.php?action=upload-plugin

To Reproduce
Steps to reproduce the behavior:

1. Build docker-container from wordpress:6.7.1-php8.2-apache
2. Upload ACF-Pro & activate plugin
3. Refresh page, get window with 'critical error'
4. Go to docker-container, and see the error log, reading like the log-message above

Expected behavior
A working ACF-Pro with PHP8.2.

I found a working solution using the proposed solution from this issue: add the code below at line 1493 in the file class-acf-field-flexible-content.php, right after the foreach:

if (!is_array($sub_field)) {
    continue;
}

Version Information:

• WordPress Version 6.71.
• PHP Version 8.2
• ACF Version 6.3.11
• Browser [e.g. chrome 103, safari 17]