Comment 21 for bug 409043

I've found the problem: sometimes an invalid number is read in persp3d_set (persp3d.cpp). This invalid value leads to an invalid point returned by box3d_get_corner_screen. When this is fed into c->lineto (to draw the box), Inkscape (correctly) crashes.
Here, I've attached a patch that checks for drawing a 3dbox side with invalid coordinates. So Inkscape doesn't crash any more.
The real fix must still be made (what to do with invalid values in persp3d_set?)
The advice for now is not to group 3dboxes it seems...