Abno queue null entry fix (vlggms#1966)

new fixed picked weight proc

code/__HELPERS/_lists.dm

@@ -316,6 +316,23 @@
 
 	return null
 
+/proc/PickWeightRealNumber(list/L)
+	var/total = 0.0
+	var/item
+	for (item in L)
+		if (!L[item])
+			L[item] = 1.0
+		total += L[item]
+	var/generator/G = generator("num", 0.0, total, UNIFORM_RAND)
+	total = G.Rand()
+	for (item in L)
+		total -= L[item]
+		if (total <= 0.000001)
+			return item
+	if(LAZYLEN(L))
+		log_runtime("PickWeightRealNumber failed with leftover total = [total]")
+	return null
+
 /proc/pickweightAllowZero(list/L) //The original pickweight proc will sometimes pick entries with zero weight.  I'm not sure if changing the original will break anything, so I left it be.
 	var/total = 0
 	var/item

code/controllers/subsystem/abnormality_queue.dm

@@ -141,7 +141,7 @@ SUBSYSTEM_DEF(abnormality_queue)
 		picked_levs |= lev
 		if(!LAZYLEN(possible_abnormalities[lev] - picking_abnormalities))
 			continue
-		var/chosen_abno = pickweight(possible_abnormalities[lev] - picking_abnormalities)
+		var/chosen_abno = PickWeightRealNumber(possible_abnormalities[lev] - picking_abnormalities)
 		picking_abnormalities += chosen_abno
 	if(!LAZYLEN(picking_abnormalities))
 		return FALSE