Ensure first error message is retrieved

src/services/Xml.php

@@ -59,7 +59,7 @@ public function generateXml(array $commerceOrders, int $pageCount): string
 			$firstFailedOrder = $failed->first();
 			$firstErrrors = $firstFailedOrder->getFirstErrors();
 			$attribute = key($firstErrrors);
-			$value = reset($firstErrrors[$attribute]);
+			$value = reset($firstErrrors);
 
 			throw new \RuntimeException("Invalid Order ID {$firstFailedOrder->getOrderId()}: {$attribute} - {$value}");
 		}