#each on undefined attributes not working anymore in 2.0.4

dfc88b4d8d1a85b743cae9476ad09397a754fe45 introduced several fixes for `#each` but broke iterating over a previously `undefined` list.

Fiddle: http://jsfiddle.net/G54Vz/

This is a regression issue and worked in 2.0.3: http://jsfiddle.net/G54Vz/1/