proj_to_vtk breaks when drainage and/or invasion algorithms present

[jgostick]

As mentioned in #2659 the io function is looking for a soln attribute on the algorithms and not finding it. Also I think it's looking for a quantity key in the settings. Basically the io function is assuming that only transport algorithms are present.

Actually, I'm wondering why it's looking for algorithms at all...I think these functions only output the network and phases?