fix(google-maps): avoid runtime error on server

The google-maps `MapInfoWindow` component currently throws
on the server because on `ngOnDestroy`, the `close()` method
is called. This method expects an instance of a Google Maps
`InfoWindow`. These cannot be created on the server.

src/google-maps/map-info-window/map-info-window.ts

@@ -114,7 +114,12 @@ export class MapInfoWindow implements OnInit, OnDestroy {
     this._eventManager.destroy();
     this._destroy.next();
     this._destroy.complete();
-    this.close();
+
+    // If no info window has been created on the server, we do not try closing it.
+    // On the server, an info window cannot be created and this would cause errors.
+    if (this.infoWindow) {
+      this.close();
+    }
   }
 
   /**