Angular 类型错误：无法读取未定义的属性

在我的Angular 2应用程序中，我收到一个错误:

无法读取未定义的属性‘Title’.

这是一个非常简单的组件，只是试图得到一个最低限度的工作在这里.它击中了我的API控制器(奇怪的是多次)，并且似乎在返回对象后击中了回调.我的控制台.日志(log)输出我期望的对象.以下是全部错误:

TypeError: Cannot read property 'title' of undefined
    at AbstractChangeDetector.ChangeDetector_About_0.detectChangesInRecordsInternal (eval at <anonymous> (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:10897:14), <anonymous>:31:26)
    at AbstractChangeDetector.detectChangesInRecords (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8824:14)
    at AbstractChangeDetector.runDetectChanges (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8807:12)
    at AbstractChangeDetector._detectChangesInViewChildren (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8877:14)
    at AbstractChangeDetector.runDetectChanges (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8811:12)
    at AbstractChangeDetector._detectChangesContentChildren (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8871:14)
    at AbstractChangeDetector.runDetectChanges (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8808:12)
    at AbstractChangeDetector._detectChangesInViewChildren (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8877:14)
    at AbstractChangeDetector.runDetectChanges (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8811:12)
    at AbstractChangeDetector.detectChanges (http://localhost:55707/lib/angular2/bundles/angular2.dev.js:8796:12)

服务(about.service.ts):

import {Http} from 'angular2/http';
import {Injectable} from 'angular2/core';
import {AboutModel} from './about.model';
import 'rxjs/add/operator/map';

@Injectable()
export class AboutService {
    constructor(private _http: Http) { }

    get() {
        return this._http.get('/api/about').map(res => {
            console.log(res.json()); // I get the error on the line above but this code is still hit.
            return <AboutModel>res.json();
        });
    }
}

组件(关于.Component.ts):

import {Component, View, OnInit} from 'angular2/core';
import {AboutModel} from './about.model';
import {AboutService} from './about.service';
import {HTTP_PROVIDERS} from 'angular2/http';

@Component({
    selector: 'about',
    providers: [HTTP_PROVIDERS, AboutService],
    templateUrl: 'app/about/about.html'
})

export class About implements IAboutViewModel, OnInit {
    public about: AboutModel;

    constructor(private _aboutService: AboutService) {}

    ngOnInit() {    
        this._aboutService.get().subscribe((data: AboutModel) => {
            this.about = data;
        });
    }
}

export interface IAboutViewModel {
    about: AboutModel;
}

指数html

<script src="~/lib/systemjs/dist/system.src.js"></script>
<script src="~/lib/angular2/bundles/router.js"></script>
<script src="~/lib/angular2/bundles/http.js"></script>
<script src="~/lib/angular2/bundles/angular2-polyfills.js"></script>
<script src="~/lib/angular2/bundles/angular2.dev.js"></script>
<script src="~/lib/es6-shim/es6-shim.js"></script>
<script>
    System.config({
        packages: {
            app: {
                format: 'register',
                defaultExtension: 'js'
            },
            rxjs: {
                defaultExtension: 'js'
            }
        },
        map: {
            rxjs: "lib/rxjs"
        }
    });
    System.import('app/boot')
            .then(null, console.error.bind(console));
</script>