Fix undefined array values being null after serialization

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "azure-devops-extension-sdk",
-  "version": "2.0.8",
+  "version": "2.0.9",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "azure-devops-extension-sdk",
-  "version": "2.0.8",
+  "version": "2.0.9",
   "description": "Azure DevOps web extension JavaScript library.",
   "repository": {
     "type": "git",

src/XDM.ts

@@ -460,6 +460,7 @@ export class XDMChannel implements IXDMChannel {
 
             var itemType = typeof item;
             if (itemType === "undefined") {
+                newObject[key] = undefined;
                 return;
             }