Only load the ECE class (including scripts) if UPE is enabled (#3489)

Author: james-allan

includes/payment-methods/class-wc-stripe-express-checkout-element.php

@@ -65,6 +65,11 @@ public function init() {
 			return;
 		}
 
+		// ECE is only available when UPE checkout is enabled.
+		if ( ! WC_Stripe_Feature_Flags::is_upe_checkout_enabled() ) {
+			return;
+		}
+
 		// Checks if Stripe Gateway is enabled.
 		if ( empty( $this->stripe_settings ) || ( isset( $this->stripe_settings['enabled'] ) && 'yes' !== $this->stripe_settings['enabled'] ) ) {
 			return;