Type narrowing in comma operator inconsistent with 5.8

## Steps to reproduce

```typescript
type Obj = {
  prop: string
}
function assertion(input: Obj | undefined): asserts input is Obj {}

function func(input: Obj | undefined): string {
  return assertion(input), input.prop;
}
```

## Behavior with `typescript@5.8`
No type errors

## Behavior with `tsgo`
```
main.ts(7,28): error TS18048: 'input' is possibly 'undefined'.
```