fix: handle undefined rejections

[alexandre-abrioux]

Winston cannot handle promise rejections if the rejected object is undefined.
A simple test is to add Promise.reject(undefined) somewhere in your app and Winston will throw the following exception:

TypeError: Cannot destructure property 'message' of 'err' as it is undefined.
    at RejectionHandler.getAllInfo (/.../node_modules/winston/lib/winston/rejection-handler.js:77:11)
    at RejectionHandler._unhandledRejection (/.../node_modules/winston/lib/winston/rejection-handler.js:168:23)

I added a test that checks for this error, and a fix that makes this test go green.