`arrays_to_dict!()` empty arrays not getting converted to empty dict

[kaarthiksundar]

This function should convert empty arrays to empty dicts but it is not doing so because of a length() != 0 filter in the if condition. Is there a specific reason for doing so?

We are doing this in GasModels explicitly in the lines https://github.com/lanl-ansi/GasModels.jl/blob/7305809e6e5a1a45f831265de70e1d6b9aae2c7d/src/io/matgas.jl#L726

@rb004f and I were thinking this should be moved to IM. Let me know.

[ccoffrin]

I don't see any reason not to add support for this. The logic in arrays_to_dicts! will need to be updated so that the isa(v[1], Dict) check does not break in the length() == 0 case. A PR is welcome and make sure to add a test for this specific case so that we don't have any regressions.