Fix arrange objectfunction to avoid last object in awkward positions.
Fix arrange objectfunction to avoid last object in awkward positions.

fixes #3900
prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r,prusa3d/Slic3r