Important: Category type icons come from the frontend icon registry 

Description 

The partner page, the partner card of the partner list, the partnerships list and the partnerships teaser show the icon of each category type of a partner. The partials Partials/Partner/Page/Categories.html, Partials/Partner/Item.html, Partials/Partnerships/List/Item.html and Partials/Partnerships/Teaser/Item.html rendered it with core:icon, from the icon registry of the TYPO3 backend. They now render it with the ab:icon ViewHelper of academic_base, from its frontend icon registry, with the arguments they had.

The identifiers stay category_types.partners.<type>, and so does the rendered markup, the inlined drawing in its wrapper <span class="t3js-icon icon" data-identifier="…"> . No icon of this extension changes its registration: category_types registers every category type icon in both registries, so the backend keeps showing the same icons. One case changes on purpose: a category type declared without an icon file made the partials fail with exception 1440754980 of the bitmap icon provider of TYPO3, which the backend icon registry picks for an empty source. It now shows TYPO3's not-found placeholder.

What the frontend shows can now differ from the backend:

• A type that declares a frontendIcon in Configuration/CategoryTypes.yaml shows that file in the frontend and its icon in the backend.
• A site package replaces the icon of a type for the frontend only by registering its identifier, for example category_types.partners.region, in its own Configuration/FrontendIcons.php.

An override of one of the partials that still renders the icons with core:icon keeps working and keeps showing the backend icon of each type. It misses a frontendIcon and a frontend replacement until it switches: replace <core:icon with <ab:icon, keep every argument, and declare xmlns:ab="http://typo3.org/ns/FGTCLB/AcademicBase/ViewHelpers" in the <html> tag of the partial.