fixed changelog paging

src/app/models/changelog.model.ts

@@ -1,6 +1,8 @@
 import {BaseModel} from './base.model';
+import {IdModel} from './id.model';
 
 export class ChangelogModel extends BaseModel {
+  _id: IdModel = null;
   date: Date;
   action: string;
   collection: string;