Fix the fatal error that occurs while processing a subscription renewal when the object is stored in the subscription's metadata.

Author: iamdharmesh

woocommerce/payment-gateway/integrations/class-sv-wc-payment-gateway-integration-subscriptions.php

@@ -448,7 +448,7 @@ public function do_not_copy_order_meta( $order_meta ) {
 		foreach ( (array) $order_meta as $index => $meta ) {
 
 			// this accounts for different versions of the Subscriptions filter running before and after WooCommerce Subscriptions 2.5
-			if ( in_array( $index, $meta_keys ) || ( isset( $meta['meta_key'] ) && in_array( $meta['meta_key'], $meta_keys ) ) ) {
+			if ( in_array( $index, $meta_keys ) || ( is_array( $meta ) && isset( $meta['meta_key'] ) && in_array( $meta['meta_key'], $meta_keys ) ) ) {
 				unset( $order_meta[ $index ] );
 			}
 		}