`Agg` should always require a `Group` node.

[xitology]

using FunSQL: SQLTable, From, Select, Get, Agg, render
person = SQLTable(:person, :person_id, :year_of_birth, :location_id)
q = From(person) |> Select(Get.person_id, Agg.count())
print(render(q))
#=>
SELECT "person_1"."person_id", COUNT(*) AS "count"
FROM "person" AS "person_1"
=#

This should instead raise an error.

[xitology]

Fixed in 5db345e.