### 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.
if (p_source.kind == GDScriptParser::DataType::BUILTIN && p_source.builtin_type == Variant::INT) {
#ifdef DEBUG_ENABLED
			if (p_source_node) {
				parser->push_warning(p_source_node, GDScriptWarning::INT_AS_ENUM_WITHOUT_CAST);
			}
#endif
			return true;
		}
		if (p_source.kind == GDScriptParser::DataType::ENUM) {
			if (p_source.native_type == p_target.native_type) {
				return true;
			}
		}
		return false;
	}
	
	if (p_source.kind == GDScriptParser::DataType::BUILTIN && p_source.builtin_type == Variant::NIL) {
		
		return true;
	}
	StringName src_native;
	Ref<Script> src_script;
	const GDScriptParser::ClassNode *src_class = nullptr;
	switch (p_source.kind) {
		case GDScriptParser::DataType::NATIVE:
			if (p_target.kind != GDScriptParser::DataType::NATIVE) {
				
				return false;
			}
			if (p_source.is_meta_type) {