add notion of "Undefined" as possible value for attribute

We need some way to test the equals on reference and attributes that haven't been defined by the user

myAsset.myRef == Undefined
myAsset.myRef != Undefined

myAsset.myattr == Undefined
myAsset.myattr != Undefined

Edited Jan 04, 2022 by Vojtisek Didier

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information

Admin message