When initializing, song does not work properly with an empty object

[HsienW]

Issue description

I refer #466
when I was initializing, song used an empty object, and then I wanted to use addPlaylist to dynamically update the playlist, but it didn't work properly, and it would generate "Uncaught (in promise) DOMException: The element has no supported sources." error

import

import amplitude from 'amplitudejs';

    constructor() {
        super();
        this.amplitude = amplitude;
    }

initializing:

this.amplitude.init({
            songs: [
                {
                    url: "" // this
                }
            ],
            callbacks: {
               ...
            }
        });

addPlaylist & play :

        this.amplitude.addPlaylist(
            'current_starting_playlist',
            {
                name: 'test',
                title: 'test',
                author: 'test'
            },
            [
                {
                    "name": "Money Changes Everything",
                    "artist": "Cyndi Lauper",
                    "album": "She's So Unusual",
                    "url": "https://p.scdn.co/mp3-preview/01bb2a6c9a89c05a4300aea427241b1719a26b06",
                    "cover_art_url": "https://i.scdn.co/image/54b3222c8aaa77890d1ac37b3aaaa1fc9ba630ae"
                },
                {
                    "name": "Pyttefolk och tigerstekar i hängmattan",
                    "artist": "Bronsåldersstadens kollaps",
                    "album": "Hot Fuss",
                    "url": "https://p.scdn.co/mp3-preview/7a785904a33e34b0b2bd382c82fca16be7060c36",
                    "cover_art_url": "https://521dimensions.com/img/open-source/amplitudejs/album-art/guidance.jpg"
                }
            ]);

        this.amplitude.play();

Environment

Version: 5.3.2

Steps to reproduce the issue

1. click " test add playlist"

What is expected?

Dynamically update current playlist

Link to where issue can be reproduced

I copied blue player and added a test add playlist dom to bind the call function.
Reproduce codepen link: https://codepen.io/hsienw/pen/yLbmpgG?editors=1111

Additional details / screenshots

[Maenny]

I have a similar problem (Just using global songs instead of playlist).

I was able to get it to work with playNow(s):

Amplitude.addSong( {song object } );
Amplitude.playNow(Amplitude.getSongs()[0]);

BUT it seems, that with this approach the callbacks won't fire...