Fix another busted upgrade - helper was wrong

constants.js

@@ -260,7 +260,7 @@ const effect_types = {
   },
   "helper": {
     "apply": function (effect, productivity, helperCount) {
-      return productivity * (1 + effect.amount * helperCount);
+      return scaleCost(productivity, 1 + effect.amount * helperCount);
     },
     "desc": function (effect) {
       return "+" + round(effect.amount * 100) + "% food/sec from " + buildings[effect.helped].name + " for every " + buildings[effect.helper].name + " owned.";