Remove parent for DropMenu
QWidget::winId() will force creating window handles for all its ancestor widgets unless the Qt::WA_DontCreateNativeAncestors flag is set.
For example, on wayland, this would result in creating sub-surfaces, and depending on the client, it's likely that there are going to be issues with painting.
On the other hand, since the DropJob takes care of setting the transient parent for the DropMenu, the parent can be simply omitted.