BUG: IndexError in libreduction
cc @WillAyd @jreback another from the groupby-Exception follow-ups.
Any easy way to summarize how this was throwing an IndexError? Not immediately apparent > Any easy way to summarize how this was throwing an IndexError? Not immediately apparent

Case where `self.bins` is empty, so `self.bins[0]` raises `IndexError`.  The `self.ngroups > 0` check is incorrect because of a kludge on L217-221 does this affect user facing code in any way? > does this affect user facing code in any way?

Not AFAICT, no. can you rebase Closing for now, I want to take a look at whats happening before we get here