### 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
String first = p_qualified_name.get_slice("::", 0);
	Vector<String> class_names;
	GDScript *result = nullptr;
	
	if (first.is_empty() || first == name) {
		class_names = p_qualified_name.split("::");
		result = this;
	} else if (p_qualified_name.begins_with(get_root_script()->path)) {
		
		class_names = p_qualified_name.trim_prefix(get_root_script()->path).split("::");
		result = get_root_script();
	} else if (HashMap<StringName, Ref<GDScript>>::Iterator E = subclasses.find(first)) {
		class_names = p_qualified_name.split("::");
		result = E->value.ptr();
	} else if (_owner != nullptr) {
		
		return _owner->find_class(p_qualified_name);