title: agm-marker's markerClick() is returning null
body: <p>From the angular google maps API, we have a markerClick() function with the following definition,</p>
  
  <pre><code> @Output() markerClick: EventEmitter&lt;void&gt; = new EventEmitter&lt;void&gt;();
  </code></pre>
  
  <p>But when I am using in my application, I am getting <strong>NULL</strong>.</p>
  
  <p>I have the following code for the application,</p>
  
  <p>In my HTML file,</p>
  
  <pre><code>&lt;agm-map [latitude]="latitude" [longitude]="longitude" [zoom]="zoom"&gt;
          &lt;agm-marker *ngFor="let marker of coordinates;" 
          [iconUrl]="icon" 
          [latitude]="marker.latitude" 
          [longitude]="marker.longitude"
          [markerClickable]="true"
          (markerClick)="markerClicked($event)"&gt;
      &lt;/agm-marker&gt;
      &lt;/agm-map&gt;
  </code></pre>
  
  <p>And in .TS file,</p>
  
  <pre><code> markerClicked($event: MouseEvent) {
      console.log('clicked'); ----------------(1)
      console.log($event);--------------------(2)
    }
  </code></pre>
  
  <p>For statement (2), I am getting NULL as the console output.
  I am expecting it to be marker Object. Is my understanding wrong? 
  How to get the lat and lng from the markerClick() function.</p>
  
  <p>Note, I am already using <strong><em>mapClick()</em></strong> function for the <strong>agm-map tag</strong>, but when I am using that function, It is not responding to clicks on already drawn markers on the Map.</p>