[NTG-context] Section head placement wrong when the after key is used

[Marco Patzer]

Hi!

In the following example the 2nd section head stays on page one when
the “after” key is used. If the blackrule is commented out the
section head moves to page two as intended.

What's the reason the section head stays on the previous page when
the “after” is used and how to fix this?

\setuphead
  [section]
  [after=\blackrule]  %% works as desired when commenting this one out

\starttext
  \startsection [title=Foo]
    \samplefile{knuth}
  \stopsection

  \startsection [title=Bar]
    \framed[height=15cm]{}
    \samplefile{knuth}
  \stopsection
\stoptext

Marco