Child events on arrays are fired on incorrect paths

If child events are bound to a path that is an array, the references in the callbacks will contain the wrong child paths

Example:
```js
// Add subscription:
db.ref('chats/chat1/members_array').on('child_added', ref => {
   console.log(ref.path); // "chats/chat1/members_array/2" instead of "chats/chat1/members_array[2]"
});
```