Fixed push undefined eror

ref #104

src/models/responses/ResponseGroupContact.ts

@@ -68,6 +68,7 @@ export class ResponseGroupContact {
         this.phone = contact.phone;
         this.email = contact.email;
         this.address = contact.address;
+        this.groups = new Array<ResponseRunnerGroup>();
         for (let group of contact.groups) {
             this.groups.push(group.toResponse());
         }