Added (string) typecast to `$prop->getValue()`' call on lib/../util/Log.php:163

[RickKukiela]

This addresses the possible bug still present in 2.0.3 which I discussed in this issue post:

https://github.com/AuthorizeNet/sdk-php/issues/458

[gnongsie]

Hi @RickKukiela,

Thank you for this PR.

Unfortunately, absorbing this change and releasing it will take some time. Kindly be patient with us.

-- Gabriel

[RickKukiela]

All good! Thanks for confirming receipt :)

[gnongsie]

Closing this PR as the fix has been added as part of a different commit. Also, I am not using type casting, in the event that it causes issues later on. Instead, I will check for null and provide an empty string if the object is null.