Allow empty componentarrays

[JTaets]

ComponentArray(a=Int[]) #fails
ComponentArray(a=Int[],b=[4,5]) #works

In my code, a can or cannot contain values. But in both cases, I would like to be able to use the same code by allowing empty componentarrays.

This line in the code prevents empty componentarrays. (reduce isn't allowed for empty arrays).

This is easily fixed by changing that line to

if length(data) == 1
    data = [data[1]]
elseif length(data) > 1
    data = reduce(vcat, data)
end

Note: type info for the array a is needed, or another error is thrown.

[JTaets]

Also Base.show(io::IO, mime::MIME"text/plain", x::ComponentVector) will need an extra if-statement to print those empty componentarrays because last_index fails

[JTaets]

Nevermind, ComponentArray{Int}(a=Int[]) works