Playlist timeline indicator only updated while mouse is moved

### Issue type

**I'm submitting a ...** (check one with "x")

* [X] bug report
* [ ] feature request
* [ ] question about the decisions made in the repository

### Issue description

Open the sample provided at http://akveo.com/ngx-admin/?utm_source=nebular_documentation&utm_medium=footer#/pages/dashboard. Start the playlist to play the first song. The timeline indicater only updates when the mouse is moved. If you do not move the mouse, the music plays, but the position indicator is not updated.

### Other information:

**npm, node, OS, Browser**
```
Chrome Version 67.0.3396.99 (64-Bit)
```