NODE_ENV is undefined, triggers console error in production

create-react-app with webpack >=4, I'm getting:
`You are currently using minified code outside of NODE_ENV === 'production'. This means that you are running a slower development build of Redux. You can use loose-envify (https://github.com/zertosh/loose-envify) for browserify or DefinePlugin for webpack (http://stackoverflow.com/questions/30030031) to ensure you have the correct code for your production build.`
From mapbox-gl-directions.js:5436 in production.
Adding process.env.NODE_ENV to the string in line 5413 results with printing _undefined_.
Adding process.env.NODE_ENV to the console.error in line 5436 results with printing 'production'.
I was wondering if there is a way to avoid this error in the log. Thanks.

Start by reproducing the warning with create-react-app and webpack >=4, then inspect mapbox-gl-directions.js around lines 5413 and 5436 to trace the differing NODE_ENV values. Compare the production build configuration with the Redux warning behavior. Done means production use no longer logs this NODE_ENV error.

Written by the indexing model from the issue text.