### 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("Remove Theme Item"));
	switch (p_data_type) {
		case Theme::DATA_TYPE_COLOR: {
			ur->add_do_method(*edited_theme, "clear_color", p_item_name, edited_type);
			ur->add_undo_method(*edited_theme, "set_color", p_item_name, edited_type, edited_theme->get_color(p_item_name, edited_type));
		} break;
		case Theme::DATA_TYPE_CONSTANT: {
			ur->add_do_method(*edited_theme, "clear_constant", p_item_name, edited_type);
			ur->add_undo_method(*edited_theme, "set_constant", p_item_name, edited_type, edited_theme->get_constant(p_item_name, edited_type));
		} break;
		case Theme::DATA_TYPE_FONT: {
			ur->add_do_method(*edited_theme, "clear_font", p_item_name, edited_type);
			if (edited_theme->has_font(p_item_name, edited_type)) {
				ur->add_undo_method(*edited_theme, "set_font", p_item_name, edited_type, edited_theme->get_font(p_item_name, edited_type));
			} else {
				ur->add_undo_method(*edited_theme, "set_font", p_item_name, edited_type, Ref<Font>());
			}
		} break;
		case Theme::DATA_TYPE_ICON: {
			ur->add_do_method(*edited_theme, "clear_icon", p_item_name, edited_type);
			if (edited_theme->has_icon(p_item_name, edited_type)) {
				ur->add_undo_method(*edited_theme, "set_icon", p_item_name, edited_type, edited_theme->get_icon(p_item_name, edited_type));
			} else {
				ur->add_undo_method(*edited_theme, "set_icon", p_item_name, edited_type, Ref<Texture2D>());
			}
		} break;