ADD: undefined value judgment

[ariafloat]

Solution of Issues #276.

In the following application,

module.exports = function(server) {
  var photocellQuery = server.where({ type: 'photocell' });
  var ledQuery = server.where({ type: 'led' });
  server.observe([photocellQuery, ledQuery], function(photocell, led){
    photocell.streams.intensity.on('data', function(m) {
      if(m.data < 0.5) {
        if (led.available('turn-on')) {
          led.call('turn-on');
        }
      } else {
        if (led.available('turn-off')) {
          led.call('turn-off');
       }
     }
   });
});}

After [led.call('turn-on');] was called, the following of [virtual_device.js] is called.

this._socket.on(logTopic, function(data) {
  self._update(data);
  self._eventEmitter.emit(data.transition);
});

But there are no "actions" properties in "data".

Therefore [this._actions = entity.actions;] will be undefined by the following of [virtual_device.js],

VirtualDevice.prototype._update = function(entity) {
  var self = this;
  Object.keys(entity.properties).forEach(function(prop) {
    self[prop] = entity.properties[prop];
  });
  this._actions = entity.actions;

  if(entity.links) {
    this._links = entity.links;
  }
};

and an error is output by [this._actions.some(function(action) {... ].

[mdobson]

@ariafloat Thanks for the pull request! We'll get to work taking a look at this today. I had a few questions on the thread for issue #276. Could you give those a quick look?

[AdamMagaluk]

Closing this PR, the underlying issue was fixed in #284