[FIX] Popup: Refresh DomRef During Closing

- when the Popup is closed and somehow its content was rerendered (e.g.
due to a destroy of a content element) the DomRef in 'fnClosed' isn't
the same anymore.
- therefore the DomRef has to be refetched and processed accordingly.

BCP: 1482003744
Change-Id: Iba61b6cbed7f89e9607608d5489cfdc6c3347cac
Merge "[FIX] Popup: Refresh DomRef During Closing"