### Godot version

4.1.dev

### System information

Win11

### Issue description

I load a non-existing GDScript, but it still returns a valid instance instead of null.
```gdscript
@tool
extends EditorScript

func _run():
	var s = ResourceLoader.load("non_exists.gd", "", ResourceLoader.CACHE_MODE_IGNORE)
	print(s)
	assert(s == null)

```

```
  Attempt to open script 'res://non_exists.gd' resulted in error 'File not found'.
<GDScript#-9223369015982753437>
  res://new_script.gd:7 - Assertion failed.

```

### Steps to reproduce

N/A

### Minimal reproduction project

N/A
struct ClassRefWithName {
		ObjectID id;
		String fully_qualified_name;
	};
	Vector<ClassRefWithName> weak_subclasses;
	
	for (KeyValue<StringName, Ref<GDScript>> &E : subclasses) {
		E.value->_owner = nullptr; 
		ClassRefWithName subclass;
		subclass.id = E.value->get_instance_id();
		subclass.fully_qualified_name = E.value->fully_qualified_name;
		weak_subclasses.push_back(subclass);
	}
	
	for (KeyValue<StringName, Ref<GDScript>> &E : subclasses) {
		p_clear_data->scripts.insert(E.value);
	}
	subclasses.clear();
	
	for (KeyValue<StringName, Variant> &E : constants) {
		GDScript *gdscr = _get_gdscript_from_variant(E.value);
		if (gdscr != nullptr) {
			p_clear_data->scripts.insert(gdscr);
		}
	}
	constants.clear();
	
	for (int i = 0; i < weak_subclasses.size(); i++) {
		ClassRefWithName subclass = weak_subclasses[i];