Port superior pick_weight implementation (#2144)

* Port superior pick_weight implementation

* Fix broken weights

code/__HELPERS/_lists.dm

@@ -392,7 +392,7 @@
 **/
 /proc/list_clear_nulls(list/list_to_clear)
 	return (list_to_clear.RemoveAll(null) > 0)
-	
+
 
 /*
  * Returns list containing all the entries from first list that are not present in second.
@@ -434,22 +434,19 @@
  * B would have a 30% chance of being picked,
  * C would have a 10% chance of being picked,
  * and D would have a 0% chance of being picked.
- * You should only pass integers in.
  */
-/proc/pick_weight(list/list_to_pick)
+/proc/pick_weight(list/list_to_pick) // monkestation edit: port superior pick_weight impl
 	var/total = 0
 	var/item
 	for(item in list_to_pick)
-		if(!list_to_pick[item])
-			list_to_pick[item] = 0
+		if(isnull(list_to_pick[item]))
+			stack_trace("weighted_pick given null weight: [json_encode(list_to_pick)]")
 		total += list_to_pick[item]
-
-	total = rand(1, total)
+	total = rand() * total
 	for(item in list_to_pick)
 		total -= list_to_pick[item]
-		if(total <= 0 && list_to_pick[item])
+		if(total <= 0)
 			return item
-
 	return null
 
 /**

monkestation/code/modules/clothing/shoes/clown.dm

@@ -20,7 +20,7 @@
 	desc = "A court jester's shoes, updated with modern squeaking technology."
 	icon_state = "jester_shoes"
 	icon = 'icons/obj/clothing/shoes.dmi'
-	squeak_sound = list('monkestation/sound/effects/clown_jingle1.ogg'=1, 'monkestation/sound/effects/clown_jingle2.ogg') //jingHONK jinglHONK jHONKgle jiHONKgle
+	squeak_sound = list('monkestation/sound/effects/clown_jingle1.ogg'=1, 'monkestation/sound/effects/clown_jingle2.ogg'=1) //jingHONK jinglHONK jHONKgle jiHONKgle
 
 /obj/item/clothing/shoes/clown_shoes/harlequin_boots
 	name = "harlequin boots"
@@ -29,4 +29,4 @@
 	icon_state = "harlequin_boots"
 	worn_icon = 'monkestation/icons/mob/clothing/feet.dmi'
 	worn_icon_state = "harlequin_boots"
-	squeak_sound = list('monkestation/sound/effects/clown_jingle1.ogg'=1, 'monkestation/sound/effects/clown_jingle2.ogg')
+	squeak_sound = list('monkestation/sound/effects/clown_jingle1.ogg'=1, 'monkestation/sound/effects/clown_jingle2.ogg'=1)