Guard against undeflined values in the map
Guard against undeflined values in the map

Use _.get to retrieve the national aggregate for total missed children
in case there is no data

https://seedscientific.atlassian.net/browse/POLIO-858

unicef/rhizome,unicef/polio,SeedScientific/polio,unicef/rhizome,SeedScientific/polio,unicef/polio,unicef/polio,SeedScientific/polio,unicef/rhizome,SeedScientific/polio,SeedScientific/polio,unicef/rhizome,unicef/polio