[ticket/12640] Preserve the active tab when previewing in posting page.

PHPBB3-12640
Merge remote-tracking branch 'prototech/ticket/12640' into develop-ascraeus

* prototech/ticket/12640:
  [ticket/12640] Preserve the active tab when previewing in posting page.
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12640] Preserve the active tab when previewing in posting page.