http-backend: Fix access beyond end of string.
http-backend: Fix access beyond end of string.

Found with valgrind while looking for Content-Length corruption in
smart http.

Signed-off-by: Tarmigan Casebolt <54dc374c49e31b8dd9ae6132f5d27147d81f0d85@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git