Remove triggers two value events

[ginovva320]

Using a value listener on a node that's being removed triggers the callback twice. The first time with an empty snapshot and a second time with the pre-deletion snapshot.

var FirebaseServer = require('firebase-server');
var s = new FirebaseServer(5000, 'dummy.firebaseio.test', {
    states: {
        CA: 'California',
        AL: 'Alabama',
        KY: 'Kentucky'
    }
});

var Firebase = require('firebase');
var client = new Firebase('ws://dummy.firebaseio.test:5000');

// Attaching a value listener to states/CA
client.child('states').child('CA').on('value', function(snap) {
    console.log('Value: ' + snap.val());
});

// After 1 second, remove states/CA
setTimeout(function() {
    console.log('Removing CA');
    client.child('states').child('CA').remove();
}, 1000);

Output:

Value: California
Removing CA
Value: null
Value: California