### Godot version

Beta 17, master

### System information

Windows 11

### Issue description

Godot gets a hard crash while attempting to code-complete for member `const` of a class.

### Steps to reproduce

```GDScript
enum E { V1 }

const e := E
```

And then type a `.` after the last `E`, which triggers code hints/auto-completion for subscripts based on `E` and causes a hard crash.

Does not happen for `var e := E.V1`.

### Minimal reproduction project

See above.
bool is_base_value_reduced = false;
	Variant base_value = make_expression_reduced_value(p_subscript->base, is_base_value_reduced);
	if (!is_base_value_reduced) {
		return Variant();
	}
	if (p_subscript->is_attribute) {
		bool is_valid = false;
		Variant value = base_value.get_named(p_subscript->attribute->name, is_valid);
		if (is_valid) {
			is_reduced = true;
			return value;
		} else {
			return Variant();
		}
	} else {
		bool is_index_value_reduced = false;