isPaymentSuccess can return undefined property error

[phillbrown]

In a standard process, isPaymentSuccess is usually called on the notification callback URL and therefore the transaction status will have been set by SagePay. However if we test that transaction endpoint without setting the status, it returns an error: Undefined property: Academe\SagePay\Model\TransactionPdo::$Status

To fix, change line 550 in TransactionAbstract.php to:

if (isset($this->Status) && ($this->Status == 'OK' || $this->Status == 'AUTHENTICATED' || $this->Status == 'REGISTERED')) {

[judgej]

Thanks. A fix has been pushed to master:

dfe42e1