bguiz/ember-sprite — pull request #2 by Piedade (2014-10-16 23:08:59+00:00)
Title: Path or pattern "assets/undefined.css" did not match any files [string exception]

This error occurs in my ember -cli v0.46 app, i did the update to v1.2 and the same error occurred.
I saw that the variable that will fetch the app name is wrong, this pull request fixed my issue.
Thanks