Hi!
Determining if an optional parameter is set or not within the configuration is sometimes rather difficult and often not functionally possible, sadly - due to zero values. Especially so with a string type and not something more simple like a boolean, I believe.
The functions you’re looking for are GetOk and its deprecated (but still used) sibling GetOkExists within the SDK.
See this other thread regarding the unfortunate pitfalls of these, though.