Blender Git Loki

Fix meta-ball bound-box calculation reading past buffer bounds

This broke "test_undo.view3d_multi_mode_select" test in
"lib/tests/ui_simulate" and is likely exposed by recent changes to
bounding box calculation.

The missing check for DL_INDEX4 dates back to code from 2002 which
intended to check this but was checking for DL_INDEX3 twice
which got removed as part of a cleaned up.

This could be hidden from memory checking tools as meta-balls
over-allocate vertex arrays.