Indexing into a multi-dimensional DimStack is broken if any layer is a nested DimArray

[tiemvanderdeure]

I'll admit I don't make objects like this every day, but definitely a bug:

a = [rand(X(1:4)) for z in Z(1:2), y in Y(1:2)]
ds = DimStack((;a))
ds1 = ds[1]
typeof(ds1)

ds1 is a 0-dimensional DimStack for some reason, where it should be just a NamedTuple with a DimArray

[tiemvanderdeure]

Not too hard to find where this one is, it even has a TODO

DimensionalData.jl/src/stack/indexing.jl

Lines 131 to 134 in de6ca6e

	newlayers = unrolled_map(f, values(s))
	# Decide to rewrap as an AbstractDimStack, or return a scalar
	if _any_dimarray(newlayers)
	# TODO rethink this for many-layered stacks

I'll have a stab at a fix