Error during order submission

Hello,

thanks for this small and helpful plugin 🙂 I have also successfully tested and installed it. However, I encountered the following error that occurs when generating the email when you submit the order in the frontend:

[22-Apr-2025 07:41:56 UTC] PHP Fatal error:  Uncaught Error: Call to a member function put_contents() on null in /home/mhnlfilweowt/staging/wp-content/plugins/sepa-qr-code-for-woocommerce/muxp-sepaqr.php:278
Stack trace:
#0 /home/mhnlfilweowt/staging/wp-content/plugins/sepa-qr-code-for-woocommerce/muxp-sepaqr.php(196): muxp_set_persistent()
#1 /home/mhnlfilweowt/staging/wp-content/plugins/sepa-qr-code-for-woocommerce/muxp-sepaqr.php(113): muxp_get_qrcode()
#2 /home/mhnlfilweowt/staging/wp-includes/class-wp-hook.php(324): muxp_email_after_order_table()
#3 /home/mhnlfilweowt/staging/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#4 /home/mhnlfilweowt/staging/wp-includes/plugin.php(517): WP_Hook->do_action()
#5 /home/mhnlfilweowt/staging/wp-content/plugins/woocommerce/templates/emails/email-order-details.php(90): do_action()
#6 /home/mhnlfilweowt/staging/wp-content/plugins/woocommerce/includes/wc-core-functions.php(345): include('/home/mhnlfilwe...')
#7 /home/mhnlfilweowt/staging/wp-content/plugins/woocommerce/includes/class-wc-emails.php(442): wc_get_template()
#8 /home/mhnlfilweowt/staging/wp-includes/class-wp-hook.php(324): WC_Emails->order_details()
#9 /home/mhnlfilweowt/staging/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()

The solution to this is in the function muxp_set_persistent after

global $wp_filesystem;

which must be added here:

require_once ABSPATH . '/wp-admin/includes/file.php';
\WP_Filesystem();

This also corresponds to the instructions here in the manual: https://developer.ww.wp.xz.cn/reference/functions/wp_filesystem/

Would be great if you could take this into account in the next update 🙂