### 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
ClassDB::bind_method(D_METHOD("_update_type_items"), &ThemeTypeEditor::_update_type_items);
	ClassDB::bind_method(D_METHOD("_pin_leading_stylebox"), &ThemeTypeEditor::_pin_leading_stylebox);
	ClassDB::bind_method(D_METHOD("_unpin_leading_stylebox"), &ThemeTypeEditor::_unpin_leading_stylebox);
	ClassDB::bind_method(D_METHOD("_change_pinned_stylebox"), &ThemeTypeEditor::_change_pinned_stylebox);
}
void ThemeTypeEditor::set_edited_theme(const Ref<Theme> &p_theme) {
	if (edited_theme.is_valid()) {
		edited_theme->disconnect("changed", callable_mp(this, &ThemeTypeEditor::_update_type_list_debounced));
	}
	edited_theme = p_theme;
	edited_theme->connect("changed", callable_mp(this, &ThemeTypeEditor::_update_type_list_debounced));
	_update_type_list();
	add_type_dialog->set_edited_theme(edited_theme);
}
void ThemeTypeEditor::select_type(String p_type_name) {