The drill only progressed missions 972, 1305 and 1308 for the player who
started it, so another player breaking the drill (the usual way on a
busy Crux Prime) got no credit for the drill objectives. The live
script (L_SKULLKIN_DRILL.lua, notifyDie) credits the killer, then also
the activator when that is someone else, which is what it does now. It
also no longer dereferences a null attacker. Removes the "Missions"
TODO.
May account for part of #1021 (Crux Prime daily smashable objectives not
tallying); needs an in-game check with two players.
Refs #1021
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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