Compatibility issue with SiteGround Optimizer

I’m trying to enable SiteGround Optimizer‘s minification feature but I keep getting this error:

Error
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Error
No se puede activar Minimización CSS

I checked my debug.log file and this is what I found:

[09-Apr-2022 17:44:35 UTC] PHP Fatal error:  Uncaught Error: Call to a member function get_cart_contents_total() on null in /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Assets/SmartButton.php:1127
Stack trace:
#0 /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Assets/SmartButton.php(378): WooCommerce\PayPalCommerce\Button\Assets\SmartButton->is_cart_price_total_zero()
#1 /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Assets/SmartButton.php(195): WooCommerce\PayPalCommerce\Button\Assets\SmartButton->render_button_wrapper_registrar()
#2 /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/ButtonModule.php(56): WooCommerce\PayPalCommerce\Button\Assets\SmartButton->render_wrapper()
#3 /home/********/public_html/wp-includes/class-wp-hook.php(307): WooCommerce\PayPalCommerce\Button\ButtonModule::WooCommerce\PayPalCommerce\Button\{closure}(Object(WP))
#4 /home/******** in /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Assets/SmartButton.php on line 1127
[09-Apr-2022 17:46:10 UTC] PHP Fatal error:  Uncaught Error: Call to a member function get_cart_contents_total() on null in /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Assets/SmartButton.php:1127
Stack trace:
#0 /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Assets/SmartButton.php(378): WooCommerce\PayPalCommerce\Button\Assets\SmartButton->is_cart_price_total_zero()
#1 /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Assets/SmartButton.php(195): WooCommerce\PayPalCommerce\Button\Assets\SmartButton->render_button_wrapper_registrar()
#2 /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/ButtonModule.php(56): WooCommerce\PayPalCommerce\Button\Assets\SmartButton->render_wrapper()
#3 /home/********/public_html/wp-includes/class-wp-hook.php(307): WooCommerce\PayPalCommerce\Button\ButtonModule::WooCommerce\PayPalCommerce\Button\{closure}(Object(WP))
#4 /home/******** in /home/********/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Assets/SmartButton.php on line 1127

When disabling the PayPal plugin everything works fine.

I already reported this issue to SiteGround Optimizer’s devs but they say everything is fine on their end.