Fixes runtime on death by decapitation

[Birdtalon]

About the pull request

Fixes two runtimes caused by passing an invalid argument type to death() it should be /datum/cause_data and we passed a /mob.

Player decapitated themselves by shooting themselves in the head.

The extra typechecks are there because I don't want to assume that cause is always going to be a mob. If it's not a mob or cause_data already then we create a cause data with mob = null so at least we're passing it correctly to death()

[2023-12-28 17:54:11.462] runtime error: death called with string cause (Unknown (as Sherri Baker)) instead of datum
 - proc name: stack trace (/proc/stack_trace)
 -   source file: code/__HELPERS/unsorted.dm,1888
 -   usr: Unknown (as Sherri Baker) (/mob/living/carbon/human)
 -   src: null
 -   usr.loc: the floor (288,32,4) (/turf/open/floor/almayer)
 -   call stack:
 - stack trace("death called with string cause...")
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): death(Unknown (as Sherri Baker) (/mob/living/carbon/human), 0, "seizes up and falls limp, thei...")
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): death(Unknown (as Sherri Baker) (/mob/living/carbon/human), null)
 - the head (/obj/limb/head): droplimb(0, 0, Unknown (as Sherri Baker) (/mob/living/carbon/human), null)
 - the head (/obj/limb/head): limb delimb(Unknown (as Sherri Baker) (/mob/living/carbon/human))
 - the head (/obj/limb/head): take damage(44, 0, 0, 0, null, /list (/list), 0, Unknown (as Sherri Baker) (/mob/living/carbon/human), -1, 0, 0)
 - the head (/obj/limb/head): take damage(44, 0, 0, 0, null, /list (/list), 0, Unknown (as Sherri Baker) (/mob/living/carbon/human), -1, -1)
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): apply damage(44, "brute", "head", 0, 0, null, 0, 0, Unknown (as Sherri Baker) (/mob/living/carbon/human), 0)
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): bullet act(the rifle bullet (/obj/projectile))
 - the M41A pulse rifle MK2 (Wiel... (/obj/item/weapon/gun/rifle/m41a): attack(Unknown (as Sherri Baker) (/mob/living/carbon/human), Unknown (as Sherri Baker) (/mob/living/carbon/human), null)
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): attackby(the M41A pulse rifle MK2 (Wiel... (/obj/item/weapon/gun/rifle/m41a), Unknown (as Sherri Baker) (/mob/living/carbon/human), /list (/list))
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): attackby(the M41A pulse rifle MK2 (Wiel... (/obj/item/weapon/gun/rifle/m41a), Unknown (as Sherri Baker) (/mob/living/carbon/human), /list (/list))
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): click adjacent(Unknown (as Sherri Baker) (/mob/living/carbon/human), the M41A pulse rifle MK2 (Wiel... (/obj/item/weapon/gun/rifle/m41a), /list (/list))
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): do click(Unknown (as Sherri Baker) (/mob/living/carbon/human), the floor (288,32,4) (/turf/open/floor/almayer), "icon-x=17;icon-y=19;left=1;but...")
 - **** (/client): Click(Unknown (as Sherri Baker) (/mob/living/carbon/human), the floor (288,32,4) (/turf/open/floor/almayer), "mapwindow.map", "icon-x=17;icon-y=19;left=1;but...")
 - 
[2023-12-28 17:54:11.465] runtime error: undefined variable /mob/living/carbon/human/var/cause_name
 - proc name: death (/mob/living/carbon/human/death)
 -   source file: code/modules/mob/living/carbon/human/death.dm,117
 -   usr: (src)
 -   src: Unknown (as Sherri Baker) (/mob/living/carbon/human)
 -   src.loc: the floor (288,32,4) (/turf/open/floor/almayer)
 -   call stack:
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): death(Unknown (as Sherri Baker) (/mob/living/carbon/human), null)
 - the head (/obj/limb/head): droplimb(0, 0, Unknown (as Sherri Baker) (/mob/living/carbon/human), null)
 - the head (/obj/limb/head): limb delimb(Unknown (as Sherri Baker) (/mob/living/carbon/human))
 - the head (/obj/limb/head): take damage(44, 0, 0, 0, null, /list (/list), 0, Unknown (as Sherri Baker) (/mob/living/carbon/human), -1, 0, 0)
 - the head (/obj/limb/head): take damage(44, 0, 0, 0, null, /list (/list), 0, Unknown (as Sherri Baker) (/mob/living/carbon/human), -1, -1)
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): apply damage(44, "brute", "head", 0, 0, null, 0, 0, Unknown (as Sherri Baker) (/mob/living/carbon/human), 0)
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): bullet act(the rifle bullet (/obj/projectile))
 - the M41A pulse rifle MK2 (/obj/item/weapon/gun/rifle/m41a): attack(Unknown (as Sherri Baker) (/mob/living/carbon/human), Unknown (as Sherri Baker) (/mob/living/carbon/human), null)
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): attackby(the M41A pulse rifle MK2 (/obj/item/weapon/gun/rifle/m41a), Unknown (as Sherri Baker) (/mob/living/carbon/human), /list (/list))
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): attackby(the M41A pulse rifle MK2 (/obj/item/weapon/gun/rifle/m41a), Unknown (as Sherri Baker) (/mob/living/carbon/human), /list (/list))
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): click adjacent(Unknown (as Sherri Baker) (/mob/living/carbon/human), the M41A pulse rifle MK2 (/obj/item/weapon/gun/rifle/m41a), /list (/list))
 - Unknown (as Sherri Baker) (/mob/living/carbon/human): do click(Unknown (as Sherri Baker) (/mob/living/carbon/human), the floor (288,32,4) (/turf/open/floor/almayer), "icon-x=17;icon-y=19;left=1;but...")
 - **** (/client): Click(Unknown (as Sherri Baker) (/mob/living/carbon/human), the floor (288,32,4) (/turf/open/floor/almayer), "mapwindow.map", "icon-x=17;icon-y=19;left=1;but...")
 - 

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Changelog

🆑
fix: Fixes a runtime on decapping one's self.
/:cl:

[fira]

well i'd argue we should rather fix it at root but if it works...