ether/etherpad-lite — pull request #1682 by mluto (2013-03-29 09:12:46+00:00)
Title: Don't error in listSessionsOfGroup when there are non-existing sessions

This implements the fix proposed by eldiddio in #1519.
Sessions which are in a `group2session` or `author2session`-entry, but are no longer existent will be logged so that the request can be answered correctly.