Comment 7 for bug 830947

This is saying that the root id is missing. Is he trying to checkout a branch with no history? (Thus trying to checkout the 'null:' revision). Or maybe it is trying to mutate the state to remove the tree root.

This is specifically triggering during "bzr checkout" so my guess is that it has to do with checking out a branch with no history.

bzr init-repo --no-trees repo
bzr init repo/branch
bzr co --lightweight repo/branch work

However, I just tried that, and it worked just fine.