Fixes cyborgs not dying when they fall into chasms (tgstation#85787)

## About The Pull Request
When a cyborg gets gibbed, its MMI pops out and is still able to talk.
Funny thing about chasms, they gib you, which leaves you still able to
talk despite the fact that you should be dead, so this nulls out the
cyborgs MMI if they fall into a chasm, leaving the player properly dead
albeit round removed
## Why It's Good For The Game
It fixes a bug that almost never happens
## Changelog
:cl:
fix: borgs no longer drop MMIs when chasmed
/:cl:

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Co-authored-by: Odairu <39929315+Odairu@users.noreply.github.com>
(cherry picked from commit 6c9cfa1)

code/datums/components/chasm.dm

@@ -212,6 +212,10 @@
 		REMOVE_TRAIT(fallen_mob, TRAIT_NO_TRANSFORM, REF(src))
 		if (fallen_mob.stat != DEAD)
 			fallen_mob.investigate_log("has died from falling into a chasm.", INVESTIGATE_DEATHS)
+			if(issilicon(fallen_mob))
+				//Silicons are held together by hopes and dreams, unfortunately, I'm having a nightmare
+				var/mob/living/silicon/robot/fallen_borg = fallen_mob
+				fallen_borg.mmi = null
 			fallen_mob.death(TRUE)
 			fallen_mob.apply_damage(300)