Hi,

After updating ConTeXt lmtx 2021.05.19 18:22, the line breaking with chinese characters does not work.

The following is a simple example:

```
% This font can be downloaded from
% https://github.com/adobe-fonts/source-han-serif/raw/release/OTF/SourceHanSerifSC_EL-M.zip
\definefontfamily[myfont][serif][sourcehanserifcn]
\setscript[hanzi]
\setupbodyfont[myfont,11pt]
\setuppapersize[A6][A6]
\starttext
北冥有鱼，其名为鲲。鲲之大，不知其几千里也；化而为鸟，其名为鹏。鹏之背，不知其几千里也；怒而飞，其翼若垂天之云。是鸟也，海运则将徙于南冥。南冥者，天池也。
\stoptext
```

The command `context` gives the following output:

Overfull \hbox (633.72849pt too wide) in paragraph at lines 7--1
<2: SourceHanSerifCN-Regular @ 11.0pt> 北冥有鱼，其名为鲲。鲲之大，不知其几千里也；化而为鸟，其名为鹏。鹏之背，不知其几千里也；怒而飞，其翼若垂天之云。是鸟也，海运则将徙于南冥。南冥者，天池也。