The treeWidget member of MainWindow could be initialized before the
body of the constructor, enabling it to be a *const variable.
Task-number: QTBUG-111228
Change-Id: If4a3b04729bc7fa5859ca88183eec376f6992455
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
(cherry picked from commit 5651be517a9f25798a051f7dd7548d40381148df)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
95ed706e82