indenting after section headings with before, after keyvals

[Sanjoy Mahajan <sanjoy@mrao.cam.ac.uk>]

The text after section headings is normally not indented, even if
\setupindenting[yes] is given -- which looks good and was a pain to get
right in my plain TeX days.  But the "don't indent that" code seems to
get confused if before= and after= values are given in the heading
setup.  

Below is a minimal example (using context 2006.07.24 10:49) showing that
the 'before' hairline is indented, and the "Indented?" text after the
'after' hairline is indented.  All is fine without the \setupindenting
or the \setuphead line.  Is there an easy fix that I missed?  I tried
throwing in \noindent into the before or after keys but no luck.

\setuphead[section][before={\hairline\blank},after={\nowhitespace\hairline}]
\setupindenting[medium,yes]

\starttext
\section{First}
Indented?
\stoptext