Merge pull request #17915 from tgstation/RemieRichards-lists

Adds a DEFAULTPICK() macro, updates an old list helper

code/__HELPERS/lists.dm

@@ -238,13 +238,7 @@
 	return r
 
 // Returns the key based on the index
-/proc/get_key_by_index(list/L, index)
-	var/i = 1
-	for(var/key in L)
-		if(index == i)
-			return key
-		i++
-	return null
+#define KEYBYINDEX(L, index) (((index <= L:len) && (index > 0)) ? L[index] : null)
 
 /proc/count_by_type(list/L, type)
 	var/i = 0
@@ -365,3 +359,6 @@
 	for(var/i = 1 to l.len)
 		if(islist(.[i]))
 			.[i] = .(.[i])
+
+//Picks from the list, with some safeties, and returns the "default" arg if it fails
+#define DEFAULTPICK(L, default) ((istype(L, /list) && L:len) ? pick(L) : default)