The problem was, that while loading saved bookmarks, updateBookmark()
was called which automatically called saveBookmarks() even if the
pointer of the new bookmark was not put into m_bookmarksList. Thus the
bookmark was deleted.

Task-number: QTCREATORBUG-9116
Change-Id: I9cbdfc854e2bfa0dc448d96233ca76ee62417fe2
Reviewed-by: Eike Ziller <eike.ziller@digia.com>