Fix collect on stateful generator

[jakobnissen]

Fixes #35530.

[jakobnissen]

The CI failure come from an an inference failure that reduces to this:

julia> h(x) = Array{typeof(x[]),0}
h (generic function with 1 method)

julia> only(Base.return_types(h, (Ref{Union{Nothing, Int}},)))
Type{Array{_A, 0}} where _A

I can try to work around it, but looking at it as a human, without understanding how the compiler works, it appears to be something that type inference ought to be able to figure out?

[jakobnissen]

Okay I decided to work around it.