title: Angular injection error AngularFirestore -> InjectionToken Platform ID`
body: <p>I'm using angularfire2 module. I have created FireQueryModule which is calling angularfire2 module. FireQueryModule I have injected in my AppModule.</p>
  
  <p>Flow:  <strong>AppModule -> FireQueryModule -> angularfire2</strong></p>
  
  <p>If I us AngularFirestore Service in my FireQueryService I'm getting an error</p>
  
  <pre><code>AppComponent_Host.ngfactory.js? [sm]:1 ERROR Error: StaticInjectorError(AppModule)[AngularFirestore -&gt; InjectionToken Platform ID]: 
    StaticInjectorError(Platform: core)[AngularFirestore -&gt; InjectionToken Platform ID]: 
      NullInjectorError: No provider for InjectionToken Platform ID!
      at NullInjector.push../node_modules/@angular/core/fesm5/core.js.NullInjector.get (core.js:979)
      at resolveToken (core.js:1232)
      at tryResolveToken (core.js:1182)
      at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:1077)
      at resolveToken (core.js:1232)
      at tryResolveToken (core.js:1182)
      at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:1077)
      at resolveNgModuleDep (core.js:9217)
      at _createClass (core.js:9270)
      at _createProviderInstance$1 (core.js:9234)
  </code></pre>
  
  <p><strong>Module Code</strong></p>
  
  <pre><code>import { NgModule, ModuleWithProviders } from '@angular/core';
  import { CommonModule } from '@angular/common';
  import { FireQueryService } from './services/firebase.service';
  import { FirebaseAppConfig, AngularFireModule } from 'angularfire2';
  import { AngularFirestoreModule } from 'angularfire2/firestore';
  import { AngularFirestore } from 'angularfire2/firestore';
  
  @NgModule({})
  export class FireQueryModule {
    static forRoot(config: FirebaseAppConfig): ModuleWithProviders {
      @NgModule({
        imports: [
          CommonModule,
          AngularFirestoreModule,
          AngularFireModule.initializeApp(config)
        ],
        providers: [AngularFirestore]
      })
      class RootModule { }
      return {
        ngModule: RootModule,
        providers: [FireQueryService]
      };
    }
  }
  </code></pre>
  
  <p><strong>Service Code</strong></p>
  
  <pre><code>@Injectable()
  export class FireQueryService {
    constructor(private db: AngularFirestore) { } // error here if i comment it works
  }
  </code></pre>
  
  <p>I'm not getting where it's breaking.</p>