What is the use case for this line of code?

[jewpaltz]

sample-code-php/PaymentTransactions/charge-credit-card.php

Line 105 in b66cc40

if ($tresponse->getErrors() != null) {

1. If the API returned OK. Why would getTransactionResponse()->getMessages() be null?
2. Would that indicate that "Transaction Failed" as the code suggests?
3. $tresponse is possibly (Possibly definitely) null. Why are you calling a method on it?