### 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
Ref<InputEventKey> k = p_event;
	if (k.is_valid()) {
		if (!k->is_pressed()) {
			return;
		}
		switch (k->get_keycode()) {
			case Key::KP_ENTER:
			case Key::ENTER: {
				_confirm_edit_theme_item();
				edit_theme_item_dialog->hide();
				edit_theme_item_dialog->set_input_as_handled();
			} break;
			case Key::ESCAPE: {
				edit_theme_item_dialog->hide();
				edit_theme_item_dialog->set_input_as_handled();
			} break;
			default:
				break;
		}
	}
}
void ThemeItemEditorDialog::_open_select_another_theme() {