Compatibility with TinyMCE 5.10.9

[Keram-Yasin]

I have tested the plugin with TinyMCE 5.10.9. I copied the files in plugin->dist->budwriter folder into a folder named budwriter inside plugins directory of the TinyMCE 5.10.9. Then I configure the tinyMCE with the following code:
budwriter: {
name: 'Andre',
photoUrl: 'https://www.example.com/images/image.png',
key: 'free4all',
socketUrl: 'http://localhost:3000'
},

Then I started the server with npm start inside server directory. The server runs good. And It could connect with the client when browse the tinyMCE client. The problem here is that the client console returned the following error:

Is this compatibility issue or I didn't followed the right steps to test the plugin?