zero on uninitialized arrays now fail in some cases

[KristofferC]

From https://s3.amazonaws.com/julialang-reports/nanosoldier/pkgeval/by_hash/0520b80_vs_997b49f/Unitful.primary.log.

Expression: zero(Vector{Union{Quantity{Float64, 𝐋}, Missing}}(undef, 1)) == [0.0m]
  UndefRefError: access to undefined reference

Looking a bit at the blame I think this was introduced in #51458.

cc @oxinabox

[KristofferC]

I think this also changed the following

# 1.10
julia> zero(Union{typeof(0.0s), Missing}[missing])
1-element Vector{Quantity{Float64, 𝐓, Unitful.FreeUnits{(s,), 𝐓, nothing}}}:
 0.0 s

# 1.11
julia> zero(Union{typeof(0.0s), Missing}[missing])
1-element Vector{Missing}:
 missing

[oxinabox]

Interesting. This certainly wasn't intended
It also effects even just Base

julia>  zero(Union{typeof(0.0), Missing}[missing])
1-element Vector{Missing}:
 missing

If we can't resolve this quickly, I think best is to revert #51458.
so as not to hold up the release, and then think about it a bit harder, for the 1.12 release

There actually is code in unitful to special case this, but it is excluded after v1.8.
So presumably there was a PR to julia that fixed that so it wasn't needed.
https://github.com/PainterQubits/Unitful.jl/blob/a09bdaac255d456e6315b77979a48956aca1d3a3/src/quantities.jl#L384-L390

[KristofferC]

Shouldn't have been closed #53602 (comment)

[KristofferC]

This seems to pass on beta now... Not really sure what fixed it.