send-email: do not muck with initial-reply-to when unset.
send-email: do not muck with initial-reply-to when unset.

When not prompting, initial_reply_to can be left unset.  Do not try to
sanitize it and get useless warning.

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