### 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
if (singleton == nullptr) {
		return;
	}
	MutexLock lock(singleton->mutex);
	if (singleton->cleared) {
		return;
	}
	singleton->cleared = true;
	RBSet<Ref<GDScriptParserRef>> parser_map_refs;
	for (KeyValue<String, GDScriptParserRef *> &E : singleton->parser_map) {
		parser_map_refs.insert(E.value);
	}
	for (Ref<GDScriptParserRef> &E : parser_map_refs) {
		if (E.is_valid())
			E->clear();
	}
	singleton->packed_scene_dependencies.clear();
	singleton->packed_scene_cache.clear();
	parser_map_refs.clear();
	singleton->parser_map.clear();
	singleton->shallow_gdscript_cache.clear();
	singleton->full_gdscript_cache.clear();
	singleton->packed_scene_cache.clear();
	singleton->packed_scene_dependencies.clear();
}
GDScriptCache::GDScriptCache() {