### 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
EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
	ur->create_action(TTR("Create Theme Item"));
	switch (p_data_type) {
		case Theme::DATA_TYPE_ICON:
			ur->add_do_method(*edited_theme, "set_icon", p_item_name, p_item_type, Ref<Texture2D>());
			ur->add_undo_method(*edited_theme, "clear_icon", p_item_name, p_item_type);
			break;
		case Theme::DATA_TYPE_STYLEBOX:
			ur->add_do_method(*edited_theme, "set_stylebox", p_item_name, p_item_type, Ref<StyleBox>());
			ur->add_undo_method(*edited_theme, "clear_stylebox", p_item_name, p_item_type);
			if (theme_type_editor->is_stylebox_pinned(edited_theme->get_stylebox(p_item_name, p_item_type))) {
				ur->add_undo_method(theme_type_editor, "_unpin_leading_stylebox");
			}
			break;
		case Theme::DATA_TYPE_FONT:
			ur->add_do_method(*edited_theme, "set_font", p_item_name, p_item_type, Ref<Font>());
			ur->add_undo_method(*edited_theme, "clear_font", p_item_name, p_item_type);
			break;
		case Theme::DATA_TYPE_FONT_SIZE:
			ur->add_do_method(*edited_theme, "set_font_size", p_item_name, p_item_type, -1);
			ur->add_undo_method(*edited_theme, "clear_font_size", p_item_name, p_item_type);
			break;
		case Theme::DATA_TYPE_COLOR: