[#32007] 2.5.x Fix admin activation from email

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32007&start=0

[#32007] Adapting George PR #3239 against staging to work against 2.5.x branch
Thanks @zero-24 ! Time to update code style and codesniffer ;-)