### 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
LineEdit *le = Object::cast_to<LineEdit>(p_control);
	if (le->get_text().strip_edges().is_empty()) {
		return;
	}
	String item_name = le->get_text().strip_edges();
	EditorUndoRedoManager *ur = EditorUndoRedoManager::get_singleton();
	ur->create_action(TTR("Add Theme Item"));
	switch (p_data_type) {
		case Theme::DATA_TYPE_COLOR: {
			ur->add_do_method(*edited_theme, "set_color", item_name, edited_type, Color());
			ur->add_undo_method(*edited_theme, "clear_color", item_name, edited_type);
		} break;
		case Theme::DATA_TYPE_CONSTANT: {
			ur->add_do_method(*edited_theme, "set_constant", item_name, edited_type, 0);
			ur->add_undo_method(*edited_theme, "clear_constant", item_name, edited_type);
		} break;
		case Theme::DATA_TYPE_FONT: {
			ur->add_do_method(*edited_theme, "set_font", item_name, edited_type, Ref<Font>());
			ur->add_undo_method(*edited_theme, "clear_font", item_name, edited_type);