depreciated ObjectId::isValid()

[gswifort]

fbfb21c

I understand that I should use not obj_id.isNull() instead of obj_id.isValid()..?
obj_id.isNull() does not return False after closing the document.

[CEXT-Dan]

Oh! The method has been marked a depreciated in 2027 SDK.

This function has performance overhead, and it's unnecessary to call isValid() 
before call functions like acdbOpenObject() and methods like 
objectClass(), database() and handle(), they will fail gracefully (without crashing) on stale id. 
To check if the id is stale or not, caller can check if originalDatabase() != nullptr.

I propose to just make our implementation call originalDatabase() != nullptr

[CEXT-Dan]

originalDatabase() != nullptr does not work in ZwCAD, I’ve restored the original call in everything but AC2027. Hopefully the test will catch any future changes