Update openfisca_core/populations/group_population.py
Update openfisca_core/populations/group_population.py

Co-authored-by: sandcha <1e3d1d967851893ec15a24bf1db4ec82f0dc8ac9@users.noreply.github.com>
openfisca/openfisca-core,openfisca/openfisca-core