I can't get count of children

I can't get count of children
come out to me undefined

```
import { AceBase } from 'acebase'
const db = AceBase.WithIndexedDB('my_db'); // browser

function fPush(){
db.ref('game/config').push({name: 'name 1' , test : 1})
}

async function getCount(){
  const valCount = await db.ref('game/config').count()
  console.log(valCount );  // undefined
}
```