UI-QT: Minor bugfix for for isosurfaces of some 3D systems. If a system has no translations of the basis cell, it can still be 3D and the isosurfaces should be drawn. This was prevented by an incorrect usage of n_cell_step, which regulates the resolution of basis cells.
UI-QT: Minor bugfix for for isosurfaces of some 3D systems.
If a system has no translations of the basis cell, it can still be 3D and the isosurfaces should be drawn. This was prevented by an incorrect usage of n_cell_step, which regulates the resolution of basis cells.

spirit-code/spirit,spirit-code/spirit,spirit-code/spirit,spirit-code/spirit,spirit-code/spirit,spirit-code/spirit