### 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_another_theme_dialog->popup_file_dialog();
}
void ThemeItemEditorDialog::_select_another_theme_cbk(const String &p_path) {
	Ref<Theme> loaded_theme = ResourceLoader::load(p_path);
	if (loaded_theme.is_null()) {
		EditorNode::get_singleton()->show_warning(TTR("Invalid file, not a Theme resource."));
		return;
	}
	if (loaded_theme == edited_theme) {
		EditorNode::get_singleton()->show_warning(TTR("Invalid file, same as the edited Theme resource."));
		return;
	}
	import_another_theme_value->set_text(p_path);
	import_other_theme_items->set_base_theme(loaded_theme);
	import_other_theme_items->reset_item_tree();
}
void ThemeItemEditorDialog::_notification(int p_what) {