Fix of an invalid extruder ID assignment after switching from a multi-material printer to a single material printer (or a printer with a lower number of extruders).
Fix of an invalid extruder ID assignment after switching from
a multi-material printer to a single material printer (or a printer
with a lower number of extruders).

prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r