### 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("Set Stylebox Item in Theme"));
	ur->add_do_method(*edited_theme, "set_stylebox", p_item_name, edited_type, p_value.is_valid() ? p_value : Ref<StyleBox>());
	if (edited_theme->has_stylebox(p_item_name, edited_type)) {
		ur->add_undo_method(*edited_theme, "set_stylebox", p_item_name, edited_type, edited_theme->get_stylebox(p_item_name, edited_type));
	} else {
		ur->add_undo_method(*edited_theme, "set_stylebox", p_item_name, edited_type, Ref<StyleBox>());
	}
	ur->add_do_method(this, "_change_pinned_stylebox");
	ur->add_undo_method(this, "_change_pinned_stylebox");
	ur->add_do_method(this, "call_deferred", "_update_type_items");
	ur->add_undo_method(this, "call_deferred", "_update_type_items");
	ur->commit_action();
}
void ThemeTypeEditor::_change_pinned_stylebox() {
	if (leading_stylebox.pinned) {
		if (leading_stylebox.stylebox.is_valid()) {
			leading_stylebox.stylebox->disconnect("changed", callable_mp(this, &ThemeTypeEditor::_update_stylebox_from_leading));
		}
		Ref<StyleBox> new_stylebox = edited_theme->get_stylebox(leading_stylebox.item_name, edited_type);
		leading_stylebox.stylebox = new_stylebox;
		leading_stylebox.ref_stylebox = (new_stylebox.is_valid() ? new_stylebox->duplicate() : Ref<Resource>());
		if (leading_stylebox.stylebox.is_valid()) {
			new_stylebox->connect("changed", callable_mp(this, &ThemeTypeEditor::_update_stylebox_from_leading));
		}
	} else if (leading_stylebox.stylebox.is_valid()) {
		leading_stylebox.stylebox->disconnect("changed", callable_mp(this, &ThemeTypeEditor::_update_stylebox_from_leading));
	}
}
void ThemeTypeEditor::_on_pin_leader_button_pressed(Control *p_editor, String p_item_name) {