HTML5 self-closing tags incorrectly become XHTML tags

I'm finding that, after going through the django-htmlmin middleware implicity self-closing tags (HTML5-style) are becoming explicity self-closed tags (XHTML-style).

For example the `` tag here…

```

```

…incorrectly becomes self-closing after going through the middleware:

```

```

Start at the django-htmlmin middleware path that transforms the shown HTML and reproduce the change from an HTML5-style tag to an XHTML-style self-closing tag. Done means HTML5 implicit self-closing tags remain unclosed after minification; compare the middleware output with the issue's examples.

Written by the indexing model from the issue text.