xAODCore: Restore (broken?) previous behavior of ShallowAuxContainer.
When we tried to access a variable in a ShallowAuxContainer and the variable exists but is empty, we were previously ignoring the ShallowAuxContainer Version and instead reading the version of the variable in the parent instead.
This should only happen in the case of an inconsistency in the input file. As a side-effect of a recent change, the behavior in this case was altered to give an error instead.
However, there do appear to be files that are broken in this way, and this change in behavior was causing problems for physics validation. Change for now to get back to the previous behavior, pending further investigation of why we're getting broken files in the first place.
Edited by Christos Anastopoulos