bug fix in JSON serialization

src/plugins/api.js

@@ -1,13 +1,15 @@
 import axios from 'axios';
+import Utils from '@/lib/Utils';
 
 const $ax = axios.create({
     baseURL: '/api/',
     transformRequest: [
         (data, headers)=>{
             if (data && !(data instanceof FormData)){
-                data = JSON.stringify(data, (k, v)=>{
+                data = Utils.deepMerge({}, data, (k, v)=>{
                     return k.startsWith('__') ? undefined : v;
-                });
+                })
+                data = JSON.stringify(data);
                 headers['Content-Type'] = 'application/json;charset=utf-8';
             }
             return data;