### 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.
p_identifier->is_constant = true;
					p_identifier->reduced_value = member.m_enum->dictionary;
					p_identifier->source = GDScriptParser::IdentifierNode::MEMBER_CONSTANT;
					return;
				}
				case GDScriptParser::ClassNode::Member::VARIABLE: {
					if (is_base && !base.is_meta_type) {
						p_identifier->set_datatype(member.get_datatype());
						p_identifier->source = GDScriptParser::IdentifierNode::MEMBER_VARIABLE;
						p_identifier->variable_source = member.variable;
						member.variable->usages += 1;
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::SIGNAL: {
					if (is_base && !base.is_meta_type) {
						p_identifier->set_datatype(member.get_datatype());
						p_identifier->source = GDScriptParser::IdentifierNode::MEMBER_SIGNAL;
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::FUNCTION: {
					if (is_base && !base.is_meta_type) {
						p_identifier->set_datatype(make_callable_type(member.function->info));
						return;
					}
				} break;
				case GDScriptParser::ClassNode::Member::CLASS: {
					reduce_identifier_from_base_set_class(p_identifier, member.get_datatype());
					return;