Make assertModelRunAndFresh() more backwards-compatible w/r/t MxModel slots.
Make assertModelRunAndFresh() more backwards-compatible w/r/t MxModel slots.

jpritikin/OpenMx,jpritikin/OpenMx,jpritikin/OpenMx,jpritikin/OpenMx,jpritikin/OpenMx,jpritikin/OpenMx