Fix #13872

std.container.make!(Array!T) now returns a reference
to an actual container, not a 'null reference' that
initializes itself upon use.

A more elegant solution would be to provide an overload for Array, but if I define it in std/container/array.d it will issue a conflict (even if the template is more specialized) and to do it in std/container/util.d would require to import std.container.array and I am not sure if we want that, because of the ongoing effort to decouple the imports in phobos. Regardless, setting length to 0 shouldn't be a problem for any struct based container constructed without arguments.