FEM: elmer writer, only write denisty if really needed, partitially revert 2d73444a66ac, unit test fix in separate commit
FEM: elmer writer, only write denisty if really needed, partitially revert 2d73444a66ac, unit test fix in separate commit
Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master