[Minor] Selectors: Sigh, another try to fix .last

lualib/lua_selectors/transforms.lua

@@ -54,13 +54,7 @@ local transform_function = {
       ['list'] = true,
     },
     ['process'] = function(inp, t)
-      local gen,param,state = fun.iter(inp)
-      local prev_state
-      repeat
-        prev_state = state
-        state = gen(param, state)
-      until state == nil
-      return prev_state,pure_type(t)
+      return fun.nth(fun.length(inp), inp),pure_type(t)
     end,
     ['description'] = 'Returns the last element',
   },