Fix get related order IDs method

changelog.txt

@@ -1,5 +1,8 @@
 *** WooCommerce Subscriptions Core Changelog ***
 
+= 7.1.2 - xxxx-xx-xx =
+* Fix - Added a check for the format when listing related subscription orders.
+
 = 7.1.1 - 2024-05-09 =
 * Fix - Resolved an issue that caused "WC_DateTime could not be converted to int" warnings to occur on non-hpos sites while editing a subscription.
 

includes/data-stores/class-wcs-related-order-store-cached-cpt.php

@@ -210,7 +210,9 @@ public function get_related_order_ids_from_cache( $subscription, $relation_type
 
 		$meta_data = $this->get_related_order_metadata( $subscription, $relation_type );
 
-		return $meta_data ? maybe_unserialize( $meta_data->meta_value ) : '';
+		$related_orders = $meta_data ? maybe_unserialize( $meta_data->meta_value ) : '';
+
+		return is_array( $related_orders ) ? $related_orders : '';
 	}
 
 	/**