placefigure: mysterious whitespace with 'rightmargin' figures

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

I tested the following on the context live.  Both figures are in the
margin, but the first and second paragraphs have a large gap between
them with figure 1 in the margin, beside the gap.  My first theory was
that the margin figure requires the whitespace (unlikely, I know).  But
that theory didn't last long: If I restore the commented-out '\input
knuth' line, then the layout has no gaps.

======================================================================
\useMPlibrary[dum]

\starttext
\input tufte 
\placefigure[rightmargin]{first}{\externalfigure[dummy]} \par
%\input knuth
\placefigure[rightmargin]{third}{\externalfigure[dummy]} \par
\input knuth
\stoptext
======================================================================


-Sanjoy

`A society of sheep must in time beget a government of wolves.'
   - Bertrand de Jouvenal