title: EmptyError: no elements in sequence
body: <p>I'm upgrading my Angular2 app from 2.0.0 to 2.3.0, and I'm running into the following error.  Any ideas as to why?  I saw this other post (<a href="https://stackoverflow.com/questions/39734085/angular-2-0-1-router-emptyerror-no-elements-in-sequence">Angular 2.0.1 Router EmptyError: no elements in sequence</a>), but after trying this, the issue still remains.  What causes this error?</p>
  
  <pre><code>Error: Uncaught (in promise): EmptyError: no elements in sequence
  Error: no elements in sequence
      at EmptyError.ZoneAwareError (zone.js:672)
      at new EmptyError (EmptyError.ts:13)
      at FirstSubscriber._complete (first.ts:161)
      at FirstSubscriber.Subscriber.complete (Subscriber.ts:122)
      at Subject._subscribe (Subject.ts:109)
      at Subject.Observable.subscribe (Observable.ts:98)
      at Observable._subscribe (Observable.ts:158)
      at Observable.subscribe (Observable.ts:98)
      at Observable._subscribe (Observable.ts:158)
      at FirstOperator.call (first.ts:82)
      at Observable.subscribe (Observable.ts:96)
      at Object.subscribeToResult (subscribeToResult.ts:32)
      at MergeAllSubscriber._next (mergeAll.ts:82)
      at MergeAllSubscriber.Subscriber.next (Subscriber.ts:95)
      at MapSubscriber._next (map.ts:80)
      at resolvePromise (zone.js:475) [angular]
      at resolvePromise (zone.js:460) [angular]
      at /libs/zone.js/dist/zone.js:509:17 [angular]
      at Object.onInvokeTask (core.umd.min.js:32) [angular]
      at ZoneDelegate.invokeTask (zone.js:261) [angular]
      at Zone.runTask (zone.js:151) [&lt;root&gt; =&gt; angular]
      at drainMicroTaskQueue (zone.js:405) [&lt;root&gt;]
      at ZoneTask.invoke (zone.js:336) [&lt;root&gt;]ErrorHandler.handleError @ core.umd.min.js:31next @ core.umd.min.js:32generatorOrNext.object.schedulerFn @ core.umd.min.js:32SafeSubscriber.__tryOrUnsub @ Subscriber.ts:238SafeSubscriber.next @ Subscriber.ts:190Subscriber._next @ Subscriber.ts:135Subscriber.next @ Subscriber.ts:95Subject.next @ Subject.ts:61EventEmitter.emit @ core.umd.min.js:32NgZone.triggerError @ core.umd.min.js:32onHandleError @ core.umd.min.js:32ZoneDelegate.handleError @ zone.js:233Zone.runGuarded @ zone.js:129_loop_1 @ zone.js:416drainMicroTaskQueue @ zone.js:425ZoneTask.invoke @ zone.js:336
  </code></pre>
  
  <p>I've also noticed that a NavigationError object is thrown when I try to change to a route that uses Guards.  But only the error above is what is shown in the console.  </p>
  
  <p><code>NavigationError {id: 2, url: "/home", error: EmptyError}</code></p>
  
  <p>I'm kind of at a loss and would appreciate any help.</p>