### Please describe the problem.

On windows, git-annex webapp reports a crash.

On the command-line, I get :

$ git annex fsck
fatal: unable to read tree 6d692a016b7d772800ddc3993ffd68fc6aaa21f3
error: invalid object 100644 39e3d739a15dc3ed11a0c324781bf3658ccb933a for '001/e8c/SHA256E-s38500--9017f32c23b4de6363d3e5105bc1c47dd3cd983e471e71e0a9d420daaf0e3e7b.html.log'
fatal: git-write-tree: error building trees
(merging origin/git-annex into git-annex...)
(recording state in git...)
git-annex: failed to read sha from git write-tree

Then, I try :

$ git annex repair
Running git fsck ...
Unpacking all pack files.

git-annex: DeleteFile ".git\\objects\\pack\\pack-c53ea32e9514b6dda95af1d8d879d91d32240d76.idx": permission denied (Accès refusé.)
failed
git-annex: repair: 1 failed


### What steps will reproduce the problem?

Dunno how that got messed up, and what to do now...

### What version of git-annex are you using? On what operating system?

latest nightly build (2015/10/19) on win 7

### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log


# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)