### 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
"trait",
		"namespace",
		"yield",
		nullptr
	};
	const char **w = _reserved_words;
	while (*w) {
		p_words->push_back(*w);
		w++;
	}
	List<StringName> functions;
	GDScriptUtilityFunctions::get_function_list(&functions);
	for (const StringName &E : functions) {
		p_words->push_back(String(E));
	}
}
bool GDScriptLanguage::is_control_flow_keyword(String p_keyword) const {
	return p_keyword == "break" ||
			p_keyword == "continue" ||
			p_keyword == "elif" ||
			p_keyword == "else" ||
			p_keyword == "if" ||
			p_keyword == "for" ||
			p_keyword == "match" ||
			p_keyword == "pass" ||
			p_keyword == "return" ||
			p_keyword == "while";
}
bool GDScriptLanguage::handles_global_class_type(const String &p_type) const {