title: RxJS forkJoin not emitting values
body: <p>I am trying to use the <code>forkJoin</code> operator to combine two observables and output a new value. One of the calls brings back an array of objects with data related to multiple people on an insurance policy (that part can't change). Another observable tells us who is logged in. I was thinking of using <code>forkJoin</code> to get both values and return the info only for the logged in user. Here's how I'm trying to build that new observable:</p>
  
  <pre><code>this.incentiveStepsHistory$ = forkJoin({
      incentiveStepsHistory: this._steps.getIncentiveStepsHistory(year),
      loggedInPerson: this._member.loggedInPerson$,
  }).pipe(
      tap((data: any) =&gt; console.log(data)),
      map((data: any) =&gt; {
          // get the data that I want
      })
      untilDestroyed(this),
  )
  </code></pre>
  
  <p>I've tried this way, as well as getting rid of the <code>this.incentiveStepsHistory$ =</code> part and just subscribing (just for testing purposes). When I do this and I check the Network tab in developer tools, I see the first call made and come back successfully. The second observable, <code>loggedInPerson</code>, is a <code>BehaviorSubject.asObservable</code> observable. When I <code>pipe</code> and <code>tap</code> in the service where that observable is created, the data is logged to the console. So both observables do work, technically.</p>
  
  <p>I've also tried the parameter of the <code>forkJoin</code> being an object like it is above, as well as passing each observable as its own parameter. No difference, everything works the same.</p>
  
  <p>The problem is that the data never comes back to the component where the <code>forkJoin</code> is created. The <code>tap</code> in the pipe shown here is never hit, and neither is the <code>map</code>. Subscribing either explicitly or via the <code>async</code> pipe in a template has the same effect: nothing is output. </p>
  
  <p>I feel like I've done it correctly, but nothing happening. Any tips are greatly appreciated.</p>