tin: article stubs one line short

When I post a new message in Tin 2.6.3, after I enter the subject
and press Enter, Tin generates the "stub" of a new article and opens
it in my editor (nvi) with `+7', which complains:

   -c option, 1: illegal address: only 6 lines in the file

And indeed, there are only six lines in the generated file:

--------------------------------- Cut ----------------------------------
From: Anton Shepelev <anton.txt@gmail.moc>
Subject: Russian encodings KOI8-RU and KOI8-R
Newsgroups: misc.test
Summary:
Keywords:

--------------------------------- Cut ----------------------------------

whereas I think there should be seven, because one empty line
separates the headers from the body, and one begins the body.  It
is rather unlikely that the error should be in Tin, but perhaps
something is wrong in my environment preventing the second empty
line in the generated stubs?

I used the following primitive wrapper script to log the process:

--------------------------------- Cut ----------------------------------
echo $* >> ~/invoke.txt
cp $2 ~/art.txt
vi $*
--------------------------------- Cut ----------------------------------