[ticket/12673] IMAGETYPE_SWC might be missing when SWC is not supported.

PHPBB3-12673
Merge remote-tracking branch 'bantu/ticket/12673' into develop-ascraeus

* bantu/ticket/12673:
  [ticket/12673] IMAGETYPE_SWC might be missing when SWC is not supported.
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12673] IMAGETYPE_SWC might be missing when SWC is not supported.