QQmlIncubator::clear crashes application when incubated component contains a ScrollBar in the Popup of a ComboBox

A customer reported an issue using QQmlIncubator to do asynchronous loading. Occasionally, they have to cancel the creation of the components, and the clear command crashes the system. They created the attached project to give a demo of the problem. When the ScrollBar within the Combo Box is commented out, the clear works and does not crash the system.