When an internal DnD occoures in IconMode, the item is moved to it's new
place but the logic in filterStartDrag() has no clue about the fact that
an internal move happend. Therefore the item gets deleted. Fix it by
changing the event's drop action to Qt::CopyAction to avoid the deletion
as it is done within QListWidget DnD code.
[ChangeLog][QtWidgets][QListView] Do not delete item on internal move.
Task-number: QTBUG-67440
Change-Id: I873d3c9fa76e107e108d9af0dcf8cecd1e18a18f
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>
c699daeceb