Undefined index error on product and shop requests with no credentials.

[AlexBa]

Hey there
I'm getting an undefined index error if I call for example:

$shopsRequest = new ShopsRequest($affilinet);
$shopsRequest->send();

The same problem appears on every product request. The reason of this problem is that I call the API with invalid credentials (to test whether the credentials are right or wrong).

It's is very easy to fix ;)