While upgrade to >=5.4 last_foreach function can get additional parameter 0 or 0s that was ok for last function, but if you try to create new calculated item with last_foreach - you will get an error of incorrect syntax
Incorrect value for field "Formula": invalid second parameter in function "last_foreach"

grpsum["Some_Group",item.key,last,0]

goes to

sum(last_foreach(/*/item.key?[group="Some_Group"],0s))

Regards, Elina