This entails selecting a model upon right-clicking if it is not selected.
Also fixed a memory leak and small tweaks.
Fixes: QDS-7401
Change-Id: I592acb3fff30ecc3236f3cf2fbe126de4fb389dc
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>