MakeProxy: Make sure a data member is created for non split object.
MakeProxy: Make sure a data member is created for non split object.

This fixes ROOT-8585

tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot