MeasureScorer null pointer exception

[Capt-Mac]

When a user has a multi rate measure that attempts to build a measureScorer per group, if one group.id does not match it tries to match on group.population.id, which is not universally populated and receives a "null pointer" exception

here is an example report that fails:
measurereport-multirate-nopopid.json

Expected behavior:
measurereport scorer calculates measurescore without error