mmap fails to preserve dimensions for zero length multi-dimensional arrays

[ancapdev]

Something like

mmap(io, Matrix{Float32}, (10, 0))

Will produce a matrix with zero size in all dimensions. I'm working with memory mapped data sets that may occasionally be empty, and I was expecting mmap to still preserve the non-zero dimensions I pass to it.

Source of the problem is here: https://github.com/JuliaLang/julia/blob/v1.7.2/stdlib/Mmap/src/Mmap.jl#L196

len == 0 && return Array{T}(undef, ntuple(x->0,Val(N)))