### 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.
reduce_cast(static_cast<GDScriptParser::CastNode *>(p_expression));
			break;
		case GDScriptParser::Node::DICTIONARY:
			reduce_dictionary(static_cast<GDScriptParser::DictionaryNode *>(p_expression));
			break;
		case GDScriptParser::Node::GET_NODE:
			reduce_get_node(static_cast<GDScriptParser::GetNodeNode *>(p_expression));
			break;
		case GDScriptParser::Node::IDENTIFIER:
			reduce_identifier(static_cast<GDScriptParser::IdentifierNode *>(p_expression));
			break;
		case GDScriptParser::Node::LAMBDA:
			reduce_lambda(static_cast<GDScriptParser::LambdaNode *>(p_expression));
			break;
		case GDScriptParser::Node::LITERAL:
			reduce_literal(static_cast<GDScriptParser::LiteralNode *>(p_expression));
			break;
		case GDScriptParser::Node::PRELOAD:
			reduce_preload(static_cast<GDScriptParser::PreloadNode *>(p_expression));
			break;
		case GDScriptParser::Node::SELF:
			reduce_self(static_cast<GDScriptParser::SelfNode *>(p_expression));
			break;
		case GDScriptParser::Node::SUBSCRIPT:
			reduce_subscript(static_cast<GDScriptParser::SubscriptNode *>(p_expression));
			break;
		case GDScriptParser::Node::TERNARY_OPERATOR:
			reduce_ternary_op(static_cast<GDScriptParser::TernaryOpNode *>(p_expression), p_is_root);
			break;
		case GDScriptParser::Node::UNARY_OPERATOR: