Netflix/RxJava — pull request #480 by zsxwing (2013-11-08 05:47:20+00:00)
Title: BugFix: Emit an IllegalArgumentException instead of ArithmeticException if the observable is empty

This PR fixed the `average` issue in #423. If an observable is empty, `average` will emit an `IllegalArgumentException` instead of `ArithmeticException`.