Bug when mixing symmetric and asymmetric conductance in different domains

[mkaguer]

Please refer to this line here

I ran into this problem when working on my lithium ion battery model. In the electrolyte phase I have diffusive-migrative conductance that is asymmetric meaning that the conductance is a Nt by 2 array. However, in the active material phase, I have pure diffusive conductance that is a Nt by 1 array. The code runs into a problem when it tries to merge these models from each domain. The bug occurs at the line I linked to above. To get around this issue, I wrote my own diffusive conductance model in the active material phase that writes it as an Nt by 2 array (where the conductance is the same for the first and second columns). I know this is how OpenPNM used to return conductances. Maybe we should revert back to this? Or be able to merge symmetric and asymmetric conductances together.