visionmedia/co — pull request #52 by jonathanong (2013-11-24 19:29:03+00:00)
Title: Fix "Generator already running" error

this is the specific case that creates the "generator already running" error. i extracted it from the other PR because that PR got too convoluted, and this occurs whether or not there is a callback supplied.

note: i would consider this a developer error. we could just throw it instead.