### 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
edited_type = p_type_name;
	bool type_exists = false;
	for (int i = 0; i < theme_type_list->get_item_count(); i++) {
		String type_name = theme_type_list->get_item_text(i);
		if (type_name == edited_type) {
			theme_type_list->select(i);
			type_exists = true;
			break;
		}
	}
	if (type_exists) {
		_update_type_items();
	} else {
		edited_theme->add_icon_type(edited_type);
		edited_theme->add_stylebox_type(edited_type);
		edited_theme->add_font_type(edited_type);
		edited_theme->add_font_size_type(edited_type);
		edited_theme->add_color_type(edited_type);
		edited_theme->add_constant_type(edited_type);
		_update_type_list();
	}
}
bool ThemeTypeEditor::is_stylebox_pinned(Ref<StyleBox> p_stylebox) {