After a `git annex copy --auto -t m3` I got this error:

    (Recording state in git...)
    error: unable to resolve reference refs/heads/git-annex: No such file or directory
    fatal: Cannot lock the ref 'refs/heads/git-annex'.
    git-annex: git [Param "update-ref",Param "refs/heads/git-annex",Param "d768b20f76ce40157214a713fb0ccb9cfc9134c2"] failed

I did a `git annex sync m3` and got

    [...]
    push m3
    Counting objects: 2976, done.
    Delta compression using up to 2 threads.
    Compressing objects: 100% (2052/2052), done.
    Writing objects: 100% (2379/2379), 392.33 KiB, done.
    Total 2379 (delta 1652), reused 460 (delta 316)
    Auto packing the repository for optimum performance.
    error: bad ref for refs/heads/git-annex
    error: bad ref for refs/heads/git-annex
    error: bad ref for refs/heads/git-annex
    To /media/m3/annex
    87c82c5..06219eb  git-annex -> synced/git-annex
    be7ff5e..6625634  master -> synced/master
    ok

And then I ran the command git-annex was trying to run:

    $ git update-ref refs/heads/git-annex d768b20f76ce40157214a713fb0ccb9cfc9134c2
    error: Trying to write ref refs/heads/git-annex with nonexistent object d768b20f76ce40157214a713fb0ccb9cfc9134c2
    fatal: Cannot update the ref 'refs/heads/git-annex'.

`git fsck --full` gives no errors.

What does this error mean?  Should I be worried?  Thanks.