Undefined Mey

Should calling and undefined method produce and error or just return NIL?

I.e. I'm too lazy to specify all "abstract" methods, but still want to use an object, so NIL looks like a good default.

Fuck. Accidentally pressed "enter", while entering title. Worse, I spilled fucking coffee on keyboard.

Worse, I smeared my wizard robe in cream that fell on my chair from the cake I was going to eat