### 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
const GDScript *current = this;
	while (current) {
		for (const KeyValue<StringName, GDScriptFunction *> &E : current->member_functions) {
			GDScriptFunction *func = E.value;
			MethodInfo mi;
			mi.name = E.key;
			if (func->is_static()) {
				mi.flags |= METHOD_FLAG_STATIC;
			}
			for (int i = 0; i < func->get_argument_count(); i++) {
				PropertyInfo arginfo = func->get_argument_type(i);
#ifdef TOOLS_ENABLED
				arginfo.name = func->get_argument_name(i);
#endif
				mi.arguments.push_back(arginfo);
			}
#ifdef TOOLS_ENABLED
			mi.default_arguments.append_array(func->get_default_arg_values());
#endif
			mi.return_val = func->get_return_type();
			r_list->push_back(mi);
		}
		if (!p_include_base) {
			return;
		}
		current = current->_base;
	}
}
void GDScript::get_script_method_list(List<MethodInfo> *r_list) const {