### 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
if (!leading_stylebox.pinned || leading_stylebox.stylebox.is_null()) {
		return;
	}
	
	edited_theme->_freeze_change_propagation();
	List<StringName> names;
	edited_theme->get_stylebox_list(edited_type, &names);
	List<Ref<StyleBox>> styleboxes;
	for (const StringName &E : names) {
		Ref<StyleBox> sb = edited_theme->get_stylebox(E, edited_type);
		
		if (sb == leading_stylebox.stylebox) {
			continue;
		}
		if (sb->get_class() == leading_stylebox.stylebox->get_class()) {
			styleboxes.push_back(sb);
		}
	}
	List<PropertyInfo> props;
	leading_stylebox.stylebox->get_property_list(&props);
	for (const PropertyInfo &E : props) {
		if (!(E.usage & PROPERTY_USAGE_STORAGE)) {
			continue;
		}