Duplication of Subject: header

Hi,

I have discovered a rather strange problem with my installation of
gpgrelay 0.959.

Some recipients were complaining that they got mails with a duplicate
Subject: header, like that:
| Received: from thorondor.akallabeth.de [127.0.0.1]
| 	by thorondor.akallabeth.de (10.0.1.201) 
| 	with SMTP (Classic Hamster Vr. 2.1 Build 2.1.0.11) ; Sat, 22 May 2010 23:39:25 +0200
| From: Thomas Hochstein <thh@...>
| To: testmail@...
! Subject: Test 3d - "Dies ist ein laengerer Test."
| Date: Sat, 22 May 2010 23:39:24 +0200
| Message-ID: <cojgv5ljbanvi8liiokuv2gtgt8dtu18gn@...>
| X-Mailer: Forte Agent 2.0/32.652
| MIME-Version: 1.0
| Content-Type: text/plain; charset=us-ascii
| Content-Transfer-Encoding: 7bit
! subject: 
| X-Relayed-By: GPGrelay Version 0.959 (Win32)
| Return-Path: <thh@...>

Something has added another - empty - header "subject:".

A bit of debugging revealed that this only happens if the Subject:
contains (a) a German umlaut (or another 8bit character) and (b)
double quotes, and that the "something" adding another "subject:"
header is indeed gpgrelay. gpgrelay seems to believe the real Subject:
header to be empty, as it doesn't trigger on "Sign" in the Subject: