Short story: draw_lamp would add itself to delayed transp drawing list from 'xray' drawing step.
This was broken, since delayed transp drawing list is always handled **before** delayed xray one.
After undo it lead to segfault crash, v3d->afterdraw_transp still having reference to old freed scene's base.
Also added asserts that those afterdraw list are empty at end of drawing step, should help
avoiding that kind of issue in future.
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