Commit 750f4bacd3262376ced3f837d8dc78f834ca233a put LV validation before
actual vg assignment. Make grub_diskfilter_make_raid to assign ->vg as
happens in other cases for consistency. Also clean up redundant code and add
explicit NULL lv->vg check in validate_lv.
Also fix segment validation in validate_lv; it became obvious when crash
was fixed.
Closes: 44199