tree ded3a2adddcb53e9220fcdbf7b6c6c1a2dbe51c0
parent 692c6b3d328e8ffbd9910d1c75431ba868dcb458
author Clark Boylan <clark.boylan@gmail.com> 1342547173 -0700
committer Clark Boylan <clark.boylan@gmail.com> 1342555588 -0700

Set change_behind to None when change is deleted.

Previously the change_ahead for the change_behind was set to None,
but then change_behind was not set to None as well. To properly
delete a change set both pointers to None.

Change-Id: If6d86759d3c10e88fca6e5f977456efd70bd0c32