uglify-js.minify failure in vis-data\peer\umd 7.1.9

[jladbury]

I use uglify.js to squelch all my third-party components into a single file. I recently upgraded vis-data to 7.1.9. uglify.js now reports an error in ...\node_modules\vis-data\peer\umd.

This is the error as reported in WebStorm debug (file13.js being vis-data/peer/umd/vis-data.js):

{
  "message": "Unexpected token: operator (?)",
  "filename": "file13.js",
  "line": 4453,
  "col": 50,
  "pos": 152249
}

and indeed if you browse there your see a double question mark: