# [NTG-context] bug? gap appears in columnset

```Hello,
We have a document where a gap occurs in a columnset under certain
conditions.
It seems to be a confluence of:```
```
- 2 sections, each with 2-column columnsets
- \page[empty] between them
- the 2nd section has a tighter interline space

The problem is that on the first page of the second section, a two-line
gap appears where gridlines 50 and 51 are.

It may be a coincidence, but 50 is also the number of lines per page in
the first section. We've found that "coincidence" to be true even with
different page and font sizes.

Can anyone tell us a way to get rid of the gap? We've tried things like
\setupcolumnsetlines[columnsetbibliography][1][1][-1]
\setupcolumnsetlines[columnsetbibliography][1][2][-1]
with various values for the last parameter, but nothing helps.

Below is a small, self-contained sample.

Lars

Version information:
This is XeTeX, Version 3.1415926-2.4-0.9998 (TeX Live 2012)
(format=cont-en 2012.11.14)  13 SEP 2013 11:38
ConTeXt  ver: 2012.05.30 11:26 MKII  fmt: 2012.11.14  int: english/english

\showgrid
\setupinterlinespace[line=12pt]
\setuplayout[grid=yes]

\definecolumnset[columnsetIntroduction0][n=2]
\setupcolumnset[columnsetIntroduction0][distance=5mm,balance=yes]

\definecolumnset[columnsetbibliography][n=2]
\setupcolumnset[columnsetbibliography][distance=5mm,balance=yes]

\starttext

\section{Introduction}

\startcolumnset[columnsetIntroduction0]
% The important thing here is how many columns of text we have.
\dorecurse {7} { \input knuth }
\stopcolumnset

\page[yes] % Always finish the current page
% If we haven't ended up on an odd page, generate an empty one.
\ifodd \pageno \else \page[empty] \fi

\section{Bibliography}
\setupinterlinespace[line=9.3pt]

\startcolumnset[columnsetbibliography]
\dorecurse {140} { \input knuth\par }
\stopcolumnset

\stoptext

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