[TYPO3-english] Get hidden object on controller

[Sergio Catalá]

I have this line in my controller:

$author = $book->getAuthor();

where field "author" is an Object that has other fields.

If I set this object to hidden in the backend, this line fails because 
the object is null.

I've read some stuff about the "setRespectEnableFields" function and set 
it to FALSE, but it seems this applies to repositories.

Can you give me a clue to get the line working despite the object is 
hidden. I want to keep allowing the backend user to hide these objects.

Thanks in advance,
Sergio