postcss: Cannot read property 'constructor' of null

At this line https://github.com/postcss/postcss/blob/master/lib/node.es6#L7

I am running into a situation where obj is null.

I was not able to build my webpack config due to this error: Cannot read property 'constructor' of null

What would cause this to happen and what might the proper fix?

I was able to add this to my local node modules to test

 if (obj === null) {
  return {};
}

Which I do no think is a good solution, but was able to build my webpack config.

Thank you for any help you maybe able to provide.