Align of empty array constructs unusable object

[yha]

julia> x = [rand(3) for _=1:0]
Vector{Float64}[]

julia> a = Align(x, 1);

julia> size(a)
ERROR: BoundsError: attempt to access 0-element Vector{Vector{Float64}} at index [1]
[...]

julia> a
Error showing value of type Align{Float64, 2, Vector{Vector{Float64}}, Tuple{True, False}}:
ERROR: BoundsError: attempt to access 0-element Vector{Vector{Float64}} at index [1]
[...]

Should probably fail at construction instead.
(similar to #25, which I think should already be closed?)

[bramtayl]

Thanks for the report! This should be closed by #33.