Undefined array key “00”

Hello,

Query Monitor shows the following error when using this plugin:

Undefined array key “00”

wp-includes/class-wp-locale.php:299
WP_Locale->get_month()
wp-includes/media.php:4498
wp_enqueue_media()
wp-content/plugins/remove-taxonomy-url/includes/class-remove-taxonomy-url-settings-api.php:56
Remove_Taxonomy_Url_Settings_API->admin_enqueue_scripts()
wp-includes/class-wp-hook.php:308
do_action(‘admin_enqueue_scripts’)
wp-admin/admin-header.php:118

Dou you have an idea, what causes the problem?

Thank you in advance for your help!
Andreas