title: ngrx/router-store - route parameter selector returns undefined for the child route
body: <p>I have this routing set up:</p>
  
  <pre><code>const SONGS_ROUTES = [
    {
      path: "songs",
      children: [
        // ...
        {
          path: "edit/:id",
          component: PerformancesComponent, // CHILD ROUTE
        },
        {
          path: "",
          component: PerformancesComponent,
        },
      ],
    },
  ];
  
  const routes: Routes = [
    {
      path: "",
      component: ConcertsComponent,
      children: [
        {
          path: "edit/:friendlyUrl",
          component: ConcertEditComponent,   // PARENT route
          children: SONGS_ROUTES,
        },
      ],
    },
  ];
  </code></pre>
  
  <p>and I need to be able to get <code>friendlyUrl</code> with ngrx selectors in every component in the tree. So I defined it as follows:</p>
  
  <pre><code>export const routerFeatureKey = "router";
  
  export const selectRouterState = createFeatureSelector&lt;
    fromRouter.RouterReducerState
  &gt;(routerFeatureKey);
  
  export const {
    selectCurrentRoute, // select the current route
    selectQueryParams, // select the current route query params
    selectQueryParam, // factory function to select a query param
    selectRouteParams, // select the current route params
    selectRouteParam, // factory function to select a route param
    selectRouteData, // select the current route data
    selectUrl, // select the current url
  } = fromRouter.getSelectors(selectRouterState);
  
  export const getSelectedConcertFriendlyUrl = selectRouteParam("friendlyUrl");
  </code></pre>
  
  <p>It does work at the "PARENT" level component (route). Which means when a user goes to <code>edit/some-concert</code> the selector returns <strong>some-concert</strong>. But for the <code>/edit/some-concert/edit/songs/1</code> (in the child component) it returns <code>undefined</code>. And I have no idea why.</p>
  
  <p>I tried both <code>routerState: RouterState.Minimal</code> and <code>routerState: RouterState.Full</code>. Same result.</p>
  
  <p>What new things can I try?</p>