Fixed display of container dock overlay if only one single visible dock area is in a container

src/FloatingDragPreview.cpp

@@ -145,6 +145,14 @@ void FloatingDragPreviewPrivate::updateDropOverlays(const QPoint &GlobalPos)
 	else
 	{
 		DockAreaOverlay->hideOverlay();
+		// If there is only one single visible dock area in a container, then
+		// it does not make sense to show a dock overlay because the dock area
+		// would be removed and inserted at the same position
+		if (1 <= VisibleDockAreas)
+		{
+			ContainerOverlay->hide();
+		}
+
 		if (DockArea == ContentSourceArea && InvalidDockWidgetArea == ContainerDropArea)
 		{
 			DropContainer = nullptr;