### Please describe the problem.
If using git annex with external .git dir webapp report a tread crashed and ever trying to restart it crash again and webapp is not able to upload/download/sync (also the download of git-annex updates is affected)

### What steps will reproduce the problem?


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

git-annex version: 5.20150113-gcf247cf
build flags: Assistant Webapp Webapp-secure Pairing Testsuite S3 WebDAV Inotify DBus DesktopNotify XMPP DNS Feeds Quvi TDFA CryptoHash
key/value backends: SHA256E SHA1E SHA512E SHA224E SHA384E SKEIN256E SKEIN512E SHA256 SHA1 SHA512 SHA224 SHA384 SKEIN256 SKEIN512 WORM URL
remote types: git gcrypt S3 bup directory rsync web bittorrent webdav tahoe glacier ddar hook external

Precompiled tarball from official git-annex download site

Gentoo linux

### Please provide any additional information below.

[[!format sh """

Launching web browser on file://../.git_annex_repos/pippo.git/annex/webapp.html      <-- note wrong path! should be /home/gioacchino/.git_annex_repos/pippo.git/annex/webapp.html

RemoteControl crashed: user error (nice ["ionice","-c3","/home/gioacchino/opt/git-annex.linux/git-annex","remotedaemon"] exited 1)

WebApp crashed: <file descriptor: 11>: hPutStr: illegal operation (handle is closed
"""]]

[[!meta title="assistant does not support nonstandard --git-dir"]]