Fixes lack of dna in old blood.

Fixes some comments about blood procs in atoms.dm
Small tweak in xeno blood blood_DNA.

code/game/atoms.dm

@@ -279,7 +279,7 @@ var/list/blood_splatter_icons = list()
 	return "\ref[initial(icon)]-[initial(icon_state)]"
 
 /atom/proc/add_blood_list(mob/living/carbon/M)
-	// Returns 1 if we had blood already
+	// Returns 0 if we have that blood already
 	if(!istype(blood_DNA, /list))	//if our list of DNA doesn't exist yet (or isn't a list) initialise it.
 		blood_DNA = list()
 	//if this blood isn't already in the list, add it
@@ -300,15 +300,17 @@ var/list/blood_splatter_icons = list()
 		return 0
 	if(!check_dna_integrity(M))		//check dna is valid and create/setup if necessary
 		return 0					//no dna!
-	return
+	return 1
 
 /obj/add_blood(mob/living/carbon/M)
-	if(..() == 0)   return 0
+	if(..() == 0)
+		return 0
 	return add_blood_list(M)
 
 /obj/item/add_blood(mob/living/carbon/M)
 	var/blood_count = blood_DNA == null ? 0 : blood_DNA.len
-	if(..() == 0)	return 0
+	if(..() == 0)
+		return 0
 	//apply the blood-splatter overlay if it isn't already in there
 	if(!blood_count && initial(icon) && initial(icon_state))
 		//try to find a pre-processed blood-splatter. otherwise, make a new one
@@ -324,13 +326,15 @@ var/list/blood_splatter_icons = list()
 	return 1 //we applied blood to the item
 
 /obj/item/clothing/gloves/add_blood(mob/living/carbon/M)
-	if(..() == 0) return 0
+	if(..() == 0)
+		return 0
 	transfer_blood = rand(2, 4)
 	bloody_hands_mob = M
 	return 1
 
 /turf/simulated/add_blood(mob/living/carbon/human/M)
-	if(..() == 0)	return 0
+	if(..() == 0)
+		return 0
 
 	var/obj/effect/decal/cleanable/blood/B = locate() in contents	//check for existing blood splatter
 	if(!B)
@@ -340,7 +344,8 @@ var/list/blood_splatter_icons = list()
 	return 1 //we bloodied the floor
 
 /mob/living/carbon/human/add_blood(mob/living/carbon/M)
-	if(..() == 0)	return 0
+	if(..() == 0)
+		return 0
 	add_blood_list(M)
 	bloody_hands = rand(2, 4)
 	bloody_hands_mob = M

code/game/objects/effects/decals/Cleanable/aliens.dm

@@ -11,7 +11,7 @@
 	icon_state = "xfloor1"
 	random_icon_states = list("xfloor1", "xfloor2", "xfloor3", "xfloor4", "xfloor5", "xfloor6", "xfloor7")
 	var/list/viruses = list()
-	blood_DNA = list()
+	blood_DNA = list("UNKNOWN DNA" = "X*")
 
 /obj/effect/decal/cleanable/xenoblood/Destroy()
 	for(var/datum/disease/D in viruses)
@@ -63,4 +63,5 @@
 
 /obj/effect/decal/cleanable/blood/xtracks
 	icon_state = "xtracks"
-	random_icon_states = null
+	random_icon_states = null
+	blood_DNA = list("UNKNOWN DNA" = "X*")

code/game/objects/effects/gibs.dm

@@ -50,11 +50,8 @@
 							gib.viruses += viruus
 							viruus.holder = gib
 
-				gib.blood_DNA = list()
 				if(MobDNA)
 					gib.blood_DNA[MobDNA.unique_enzymes] = MobDNA.blood_type
-				else if(istype(src, /obj/effect/gibspawner/xeno))
-					gib.blood_DNA["UNKNOWN DNA"] = "X*"
 				else if(istype(src, /obj/effect/gibspawner/generic)) // Probably a monkey
 					gib.blood_DNA["Non-human DNA"] = "A+"
 				var/list/directions = gibdirections[i]

code/game/turfs/simulated/dirtystation.dm

@@ -10,6 +10,7 @@
 /obj/effect/decal/cleanable/blood/old/New()
 	..()
 	icon_state += "-old"
+	blood_DNA["Non-human DNA"] = "A+"
 
 /obj/effect/decal/cleanable/blood/gibs/old
 	name = "old rotting gibs"
@@ -19,6 +20,7 @@
 	..()
 	icon_state += "-old"
 	dir = pick(1,2,4,8)
+	blood_DNA["Non-human DNA"] = "A+"
 
 /obj/effect/decal/cleanable/vomit/old
 	name = "crusty dried vomit"