Update the clearWorkArea function so that it doesn't error if there was
never a work area set up to begin with. This was causing the `npm test`
target to end with an error code.
The package-lock.json update happens on a fresh install with node 15, so
I'm including it here to make sure that the tests passing is
reproducible. I also updated the package.json file to warn you if you're
not running node 15.
