Null currency error when the Aelia currency switcher plugin is active (467)

[AlexP11223]

When the Aelia currency switcher plugin is active and configured, manually creating a WooCommerce order from the backend causes a white page with a fatal error:

PHP Fatal error Uncaught TypeError: Return value of WooCommerce\PayPalCommerce\ApiClient\ApiModule::WooCommerce\PayPalCommerce\ApiClient\{closure}() must be of the type string, null returned in /var/www/html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-api-client/services.php:325

Stack trace:

#0 /var/www/html/wp-content/plugins/woocommerce-paypal-payments/vendor/dhii/containers/src/DelegatingContainer.php(117): WooCommerce\PayPalCommerce\ApiClient\ApiModule::WooCommerce\PayPalCommerce\ApiClient\{closure}(Object(Dhii\Container\DelegatingContainer))
#1 /var/www/html/wp-content/plugins/woocommerce-paypal-payments/vendor/dhii/containers/src/DelegatingContainer.php(56): Dhii\Container\DelegatingContainer->invokeFactory(Object(Closure))
#2 /var/www/html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-api-client/services.php(319): Dhii\Container\DelegatingContainer->get('api.shop.curren...')
#3 /var/www/html/wp-content/plugins/woocommerce-paypal-payments/vendor/dhii/containers/src/DelegatingContainer.php( in /var/www/html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-api-client/services.php on line 325

To Reproduce

1. Install & configure Aelia currency switcher plugin
2. Create WooCommerce order manually from backend
3. Page will remain empty and error message is thrown instead of the “edit product page”

Possible cause

Aelia plugin modifies currency using filters and may return null.

Suggested solution

Use get_option('woocommerce_currency').

https://wordpress.org/support/topic/manual-add-order-error/#post-15190717