Set current tab as parent for duplicated tab
Summary: BUG: 408518
Test Plan: Duplicate tab, the change is visible in TreeView of Vertical Tabs plugin.
Reviewers: Falkon, drosca
Reviewed By: Falkon, drosca
Subscribers: falkon, drosca
Tags: Falkon
Differential Revision: https://phabricator.kde.org/D24933