react-meteor-data: handle.ready() is always false

According to the docs, this should work:

```js
const listLoading = useTracker(() => {
// Note that this subscription will get cleaned up
// when your component is unmounted or deps change.
const handle = Meteor.subscribe('todoList', listId);
return !handle.ready();
}, [listId]);
```

However, if I try it out, the returned value is always true, i.e. ready() is always false.

Start by reproducing the issue from the useTracker example with Meteor.subscribe('todoList', listId), then trace how the returned subscription handle reaches handle.ready(). Compare the observed state with the documented expectation and verify that ready() reports the subscription's actual readiness without breaking cleanup when the component unmounts or listId changes.

Written by the indexing model from the issue text.