Breaking: #24186 - HTMLparser - fixAttrib.[‘class’].list does not assign first element, when attribute value not in list

See Issue #24186

Description

The HTMLparser now assigns the first class of fixAttrib.class.list when none of the given class name values are found in the configured list. Until now the class attribute of the rendered HTML tag was just empty in that case.

Impact

A HTML element that had no class before could now have been assigned a class.

Migration

Add a class from the configured list to the HTML element or add a class at the first position of fixAttrib.class.list.