CKEditor 5 moves some classes in the a tag

Problem/Motivation

CKEditor 5 moves the “glightbox” class to another position.

Steps to reproduce

- In the source code I insert:

<!-- Simple image -->
<a href="large.jpg" class="glightbox">
<img src="small.jpg" alt="image" />
</a>

- I save, check the source code and find:

<!-- Simple image -->
<a href="large.jpg">
<img class="glightbox" src="small.jpg" alt="image">&nbsp;
</a>

CKEditor moved the glightbox class from the first to the second image and added &nbsp at the end.