Fixes #575 NPE when synchronize
Created originally on Bitbucket by colin-hurley (Colin Hurley)
Was already merged in Bitbucket before import, marked as merged by the import user
The condition for omitting the outgoing overlay has been adjusted to check for WorkingChangeSet. This class is the common ancestor of both uncommitted changeset implementations (GroupedUncommittedChangeSet and UncommittedChangeSet).