fix NaturalIntelligence#126: check for Array type

Author: amitguptagwl

package.json

@@ -1,6 +1,6 @@
 {
   "name": "fast-xml-parser",
-  "version": "3.12.5",
+  "version": "3.12.6",
   "description": "Validate XML or Parse XML to JS/JSON very fast without C/C++ based libraries",
   "main": "./src/parser.js",
   "scripts": {

src/xmlNode.js

@@ -7,7 +7,7 @@ module.exports = function(tagname, parent, val) {
     this.attrsMap = {};//attributes map
     this.val = val;//text only
     this.addChild = function(child) {
-        if (this.child[child.tagname]) {//already presents
+        if ( Array.isArray(this.child[child.tagname]) ){//already presents
             this.child[child.tagname].push(child);
         } else {
             this.child[child.tagname] = [child];