title: Subscribing to a Selector returns Undefined
body: <p>I have a selector that feeds info to a child. The selector works and the child component is built properly however, I wanted to subscribe to the selector in the parent component and use the information for a different task but the subscribe returns an undefined value. Can anyone point out where I am going wrong? </p>
  
  <p>Code: </p>
  
  <pre><code>size: any;
  mySubscription: Subscription;
  
  constructor(
      private AppStore: Store&lt;Store.NewState&gt;
    ) { }
  
    ngOnInit() {
         this.position$ = this.AppStore.select(positionSelectors.selectPositionState);
         if (!this.position$ === undefined) {
           this.mySubscription = this.position$.subscribe((resp) =&gt; {
           this.size = Object.keys(resp).length;
          } );
          this.mySubscription.unsubscribe();
         }
    }
  </code></pre>
  
  <p>So I am trying to get the length of the response however, nothing makes it past the conditional. If I remove it I get a bunch of errors stating that the Object is undefined.
  The specific error is: </p>
  
  <pre><code>TypeError: Cannot convert undefined or null to object
  </code></pre>