title: Dagger 2 injection returns null in Activity scope
body: <p>I need to inject a dependency that requires FragmentManager in the constructor. In order to do that, I have created a custom scope for my activity linked to the MainModule of the app. After the injection, the dependency returns null. I think the problem is in submodules because the App dependencies work fine.</p>
  
  <p>The code is the following:</p>
  
  <p><strong>HomeModule</strong></p>
  
  <pre><code>@Module
  public class HomeModule {
  
  private HomeActivity homeActivity;
  
  public HomeModule(HomeActivity homeActivity) {
      this.homeActivity = homeActivity;
  }
  
  @Provides
  public BackStackManager provideBackStackManager(){
      return new BackStackManager(homeActivity.getSupportFragmentManager());
  }
  }
  </code></pre>
  
  <p><strong>HomeScope</strong></p>
  
  <pre><code>@Scope
  @Retention(RetentionPolicy.RUNTIME)
  public @interface HomeScope {
  }
  </code></pre>
  
  <p><strong>HomeComponent</strong></p>
  
  <pre><code>@HomeScope
  @Subcomponent(modules = {HomeModule.class})
  public interface HomeComponent {
      void inject(HomeActivity activity);
  }
  </code></pre>
  
  <p><strong>ApplicationClass</strong></p>
  
  <pre><code>public HomeComponent plusHomeComponent(HomeModule homeModule){
  
      if (homeComponent == null){
          homeComponent = mainComponent.plusHomeComponent(homeModule);
      }
  
      return homeComponent;
  }
  </code></pre>