Persistent index handling in QAbstractItemModel is wrong

QTreeWidget * tree = new QTreeWidget;

// Top level node:
QTreeWidgetItem * toplevel = new QTreeWidgetItem({"toplevel"});
tree->addTopLevelItem(toplevel);
QModelIndex firstIndex = tree->model()->index(0, 0);

// Add two children:
QTreeWidgetItem * child1 = new QTreeWidgetItem({"child1"}),
                * child2 = new QTreeWidgetItem({"child2"});
toplevel->addChildren({child1, child2});
tree->expandAll();

// Select child2
tree->selectionModel()->select(tree->model()->index(1, 0, firstIndex),
                               QItemSelectionModel::Select);

// Remove child1:
tree->model()->removeRows(0, 1, firstIndex);