### 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
return OK;
	}
#endif
	{
		String source_path = path;
		if (source_path.is_empty()) {
			source_path = get_path();
		}
		Ref<GDScript> cached_script = GDScriptCache::get_cached_script(source_path);
		if (!source_path.is_empty() && cached_script.is_null()) {
			MutexLock lock(GDScriptCache::singleton->mutex);
			GDScriptCache::singleton->shallow_gdscript_cache[source_path] = Ref<GDScript>(this);
		}
	}
	bool can_run = ScriptServer::is_scripting_enabled() || is_tool();
#ifdef TOOLS_ENABLED
	if (p_keep_state && can_run && is_valid()) {
		_save_old_static_data();
	}
#endif
	valid = false;
	GDScriptParser parser;
	Error err = parser.parse(source, path, false);
	if (err) {
		if (EngineDebugger::is_active()) {
			GDScriptLanguage::get_singleton()->debug_break_parse(_get_debug_path(), parser.get_errors().front()->get().line, "Parser Error: " + parser.get_errors().front()->get().message);
		}
		
		_err_print_error("GDScript::reload", path.is_empty() ? "built-in" : (const char *)path.utf8().get_data(), parser.get_errors().front()->get().line, ("Parse Error: " + parser.get_errors().front()->get().message).utf8().get_data(), false, ERR_HANDLER_SCRIPT);
		reloading = false;