Fix double declaration of 'result'

lib/cartodb/models/dataview/formula.js

@@ -108,13 +108,13 @@ module.exports = class Formula extends BaseDataview {
         return callback(null, formulaSql);
     }
 
-    format (result) {
+    format (res) {
         const {
             result = 0,
             nulls_count = 0,
             nans_count = 0,
             infinities_count = 0
-        } = result.rows[0] || {};
+        } = res.rows[0] || {};
 
         return {
             operation: this.operation,