### 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
import_items_tree->clear();
	TreeItem *root = import_items_tree->create_item();
	if (base_theme.is_null()) {
		return;
	}
	String filter_text = import_items_filter->get_text();
	List<StringName> types;
	List<StringName> names;
	List<StringName> filtered_names;
	base_theme->get_type_list(&types);
	types.sort_custom<StringName::AlphCompare>();
	int color_amount = 0;
	int constant_amount = 0;
	int font_amount = 0;
	int font_size_amount = 0;
	int icon_amount = 0;
	int stylebox_amount = 0;
	tree_color_items.clear();
	tree_constant_items.clear();
	tree_font_items.clear();
	tree_font_size_items.clear();
	tree_icon_items.clear();
	tree_stylebox_items.clear();
	for (const StringName &E : types) {
		String type_name = (String)E;
		Ref<Texture2D> type_icon;
		if (E == "") {
			type_icon = get_theme_icon(SNAME("NodeDisabled"), SNAME("EditorIcons"));