Drag'n'drop target folders were switiching between open and closed state.
The fix changes this behaviour to only expanding the previously closed fodler
items and not changing the state of the expanded ones.
Simply passing the DragMoveEvent to QTreeView::dragMoveEvent only for closed
folder items was not enough, because QTreeView:timerEvent (which is actived
by timer set up in QTreeView::timerEvent) don't track the item which caused
the starting of the timer. So sometimes passing the mouse cursor over the
closed folder and stopping in over the expanded folder makes the expanded one
to close.
BUG: 377023