Confirm closing muliple tabs.
Summary: BUG: 380963
Test Plan:
Reviewers: dhaumann, Kate, sars, cullmann, ngraham
Reviewed By: Kate, cullmann, ngraham
Subscribers: loh.tar, emateli, mwolff, ngraham, pino, kwrite-devel
Tags: Kate
Differential Revision: https://phabricator.kde.org/D17599