## Summary

PDF export of a document with an `<include>`'d document containing an `<hlink>` at the start of a line fails to produce a clickable hyperlink.


## Steps to reproduce the bug

- Create new document named `book.tm`.

- Create new document named `c1.tm` in same directory.

- Add `<hlink|foo|https://gnu.org>` to some line in `c1.tm` (e.g. via "Insert -> Link -> Hyperlink"). Save.

- Add `bar<hlink|baz|https://gnu.org>` to some line in `c1.tm` (Note the `bar`.). Save.

- Include `c1.tm` into `book.tm` by running "Insert -> Link -> Include" and selecting `c1.tm`. Save.

- Update `book.tm` by opening `book.tm` and running "Document -> Update -> All"

- Export a PDF by running "File -> Export -> PDF". Export to file `book.pdf`.

- Open `book.pdf` in Firefox 97.0.2 or Evince 40.4.


## Expected result

Both `foo` and `baz` should be clickable hyperlinks in the exported PDF.


## Actual result

Although `baz` is is a clickable hyperlink in the PDF, `foo` is not.


## Environment

- TeXmacs version 2.1.1 (SVN revision Custom 13828) running on Pop!_OS 21.10 .

  - (if relevant) Ghostscript 9.54.0

- TeXmacs version 2.1.1 (SVN revision Custom 13828) running on Windows 10 .

## Workaround

Add some text (e.g. `bar` in the example above) immediately before the `<hlink>` tag so the tag isn't at the start of a line.