vis network with Polymer 3 on Chrome TypeError: Cannot set property 'vis' of undefined at webpackUniversalModuleDefinition

[David]

Starting point : Polymer3 starter-kit as described here : https://pwa-starter-kit.polymer-project.org/setup

with

git clone --depth 1 https://github.com/Polymer/pwa-starter-kit my-app
cd my-app

then i installed vis with "npm install --save vis"

I run it with 'npm run start'

My network is shown in Firefox 66, but in Chrome 73, I got this error

vis.js:26 Uncaught (in promise) TypeError: Cannot set property 'vis' of undefined
    at webpackUniversalModuleDefinition (vis.js:26)
    at vis.js:26

it looks that the root is undefind with Polymer and the modules so I added this two lines

	else if (typeof exports == 'undefined' && typeof module == 'undefined'&& typeof define == 'undefined')
      window['vis'] =  factory();

in webpackUniversalModuleDefinition of vis.js, like that

	if(typeof exports === 'object' && typeof module === 'object')
		module.exports = factory();
	else if(typeof define === 'function' && define.amd)
		define([], factory);
	else if(typeof exports === 'object')
		exports["vis"] = factory();
	else if (typeof exports == 'undefined' && typeof module == 'undefined'&& typeof define == 'undefined')
      window['vis'] =  factory();
  else
		root["vis"] = factory();

here is the result after modification https://spoggyfr.netlify.com/
and the source is here https://github.com/scenaristeur/spoggyfr

and the network appear in Chrome. Do you think it is a problem with vis ? Polymer ? Webpack ?
Thanks