edx/edx-platform — pull request #4888 by auraz (2014-08-19 13:26:17+00:00)
Title: Render only existing children in staff view of split_test.

This fixes BLD-1224.

Root cause is that group_id_to_child contains deleted groups.
Other solution is to clean group_id_to_child of split_test when group was deleted from group configuration page. But this will affect publishing. So this solution was skipped.

@tymofij please review.