### 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.
mark_node_unsafe(p_for->list);
		}
		if (list_type.is_variant()) {
			variable_type.kind = GDScriptParser::DataType::VARIANT;
			mark_node_unsafe(p_for->list);
		} else if (list_type.has_container_element_type()) {
			variable_type = list_type.get_container_element_type();
			variable_type.type_source = list_type.type_source;
		} else if (list_type.is_typed_container_type()) {
			variable_type = list_type.get_typed_container_type();
			variable_type.type_source = list_type.type_source;
		} else if (list_type.builtin_type == Variant::INT || list_type.builtin_type == Variant::FLOAT || list_type.builtin_type == Variant::STRING) {
			variable_type.type_source = list_type.type_source;
			variable_type.kind = GDScriptParser::DataType::BUILTIN;
			variable_type.builtin_type = list_type.builtin_type;
		} else if (list_type.builtin_type == Variant::VECTOR2I || list_type.builtin_type == Variant::VECTOR3I) {
			variable_type.type_source = list_type.type_source;
			variable_type.kind = GDScriptParser::DataType::BUILTIN;
			variable_type.builtin_type = Variant::INT;
		} else if (list_type.builtin_type == Variant::VECTOR2 || list_type.builtin_type == Variant::VECTOR3) {
			variable_type.type_source = list_type.type_source;
			variable_type.kind = GDScriptParser::DataType::BUILTIN;
			variable_type.builtin_type = Variant::FLOAT;
		} else if (list_type.builtin_type == Variant::OBJECT) {
			GDScriptParser::DataType return_type;
			List<GDScriptParser::DataType> par_types;
			int default_arg_count = 0;
			bool is_static = false;
			bool is_vararg = false;
			if (get_function_signature(p_for->list, false, list_type, CoreStringNames::get_singleton()->_iter_get, return_type, par_types, default_arg_count, is_static, is_vararg)) {