To write a program is to deal with uncertainty. Sometimes it feels like there's nothing we can count on and null (or undefined) is as pervasive as any other construct in our languages. However this does not have to be! LambdaCast dives into the thorny problem of null, and more broadly the potential for values not to exist and offers up some alternatives.
Aaron's "and then" reference: https://www.youtube.com/watch?v=CkdyU_eUm1U