it could work

code/modules/mob/living/carbon/life.dm

@@ -362,7 +362,7 @@
 		return
 
 	// Also no decay if corpse chilled or not organic/undead
-	if(bodytemperature <= T0C-10 || (!(MOB_ORGANIC in mob_biotypes) && !(MOB_UNDEAD in mob_biotypes)))
+	if((bodytemperature <= T0C-10) || !(mob_biotypes & (MOB_ORGANIC|MOB_UNDEAD)))
 		return
 
 	// Wait a bit before decaying

code/modules/mob/living/death.dm

@@ -25,7 +25,7 @@
 
 /mob/living/proc/spawn_gibs(with_bodyparts, atom/loc_override)
 	var/location = loc_override ? loc_override.drop_location() : drop_location()
-	if(MOB_ROBOTIC in mob_biotypes)
+	if((MOB_ROBOTIC) in (mob_biotypes))
 		new /obj/effect/gibspawner/robot(location, src, get_static_viruses())
 	else
 		new /obj/effect/gibspawner/generic(location, src, get_static_viruses())