debathena-msmtp constructs useless From lines for non-null instances

[jdreed]

If I run sendmail -t (or, more specifically, if I run a script that in turn runs sendmail -t), and a From: line is not specified, I get mail that looks like this:

Received: from localhost (INFINITE-LOOP.MIT.EDU [18.152.1.6])
	(authenticated bits=0)
        (User authenticated as jdreed/root@ATHENA.MIT.EDU)
	by outgoing.mit.edu (8.13.6/8.12.4) with ESMTP id p1L24wU6009311
	for <jdreed@mit.edu>; Sun, 20 Feb 2011 21:04:58 -0500 (EST)
Date: Sun, 20 Feb 2011 21:04:58 -0500 (EST)
From: jdreed/root@MIT.EDU
Message-Id: <201102210204.p1L24wU6009311@outgoing.mit.edu>
To: jdreed@mit.edu

While the address is not invalid, it's entirely useless.