In plain JavaScript, 'foo' + null == 'foonull'. This isn't always what you want, but in the vast majority of cases if you're creating a string, it's:

1) For displaying to the user

2) Generating a CSS class or something to that effect

In both of these cases the above is quite a reasonable behavior, and will never cause a runtime exception, and very rarely even a business-logic error. But if I'm working with the result of a .find() or a maybe-property on an object type, I now have to add null checks (or at best || '' fallbacks) everywhere, muddling up my code and making it harder to follow.