### Godot version

v4.0.beta.custom_build [eaf306e0b]

### System information

Windows 10

### Issue description

Selecting a `Window` node in the Editor's SceneTree results in the message
```
editor/editor_data.cpp:1058 - Parameter "p_node" is null.
```
and the Inspector shows empty content instead of the Window's properties.

I would expect, that clicking on a node in the SceneTree lets me edit the properties of the node.

Bisecting shows that this behavior got introduced in #71770

### Steps to reproduce

1. Create a Window node
2. Click on the Window node in the Editor's SceneTree

### Minimal reproduction project

N/A
}
			has_any_items = true;
		}
	}
	
	TreeItem *selected_item = edit_type_list->get_selected();
	if (selected_item) {
		if (!has_any_items) {
			edit_items_message->set_text(TTR("This theme type is empty.\nAdd more items to it manually or by importing from another theme."));
			edit_items_message->show();
		} else {
			edit_items_message->set_text("");
			edit_items_message->hide();
		}
	}
}
void ThemeItemEditorDialog::_item_tree_button_pressed(Object *p_item, int p_column, int p_id, MouseButton p_button) {
	if (p_button != MouseButton::LEFT) {
		return;
	}
	TreeItem *item = Object::cast_to<TreeItem>(p_item);
	if (!item) {
		return;
	}
	switch (p_id) {
		case ITEMS_TREE_RENAME_ITEM: {
			String item_name = item->get_text(0);
			int data_type = item->get_parent()->get_metadata(0);
			_open_rename_theme_item_dialog((Theme::DataType)data_type, item_name);
			_update_edit_item_tree(edited_item_type);