2D Simulation plots lack PML

[tylerflex]

Encountered an issue where the sim.plot() was missing PMLs for a 2D simulation. Inspecting the Simulation._make_pml_boxes(), it seems the boxes have size 0 in the normal direction, so they probably are just not being found. We can put a condition to expand the PML boxes to infinity if any of the Simulation.size is 0 along that dimension perhaps.

[momchil-flex]

Sorry, I'm confused, you mean PML along the dimension where the size is 0? That's not a good setup, in fact I think we even warn about it?

[momchil-flex]

#693

[tylerflex]

No, take a look at the PR: #830

It just adds some thickness to the pml boxes for plotting only along the dimensions where sim.size == 0.

[momchil-flex]

Oh ok.