navbar empty when state's data object has incorrect up property

When a state has an `up` property defined on its `data` object and the specified state does not exist, the script breaks and hence the navbar fails to compile (and appears empty).

```
$stateProvider.state('app', {
  url: '/',
  templateUrl: 'table.html',
  data: {
    up: 'asdfgh'
  }
});
```

```
TypeError: Cannot read property 'data' of null
    at getTitleFromState (http://localhost:9000/bradypodion.js:196:37)
    at http://localhost:9000/bradypodion.js:234:34
    at publicLinkFn (http://localhost:9000/bower_components/angular/angular.js:5586:29)
    at http://localhost:9000/bradypodion.js:213:11
    at nodeLinkFn (http://localhost:9000/bower_components/angular/angular.js:6271:13)
    at compositeLinkFn (http://localhost:9000/bower_components/angular/angular.js:5678:15)
    at publicLinkFn (http://localhost:9000/bower_components/angular/angular.js:5587:30)
    at http://localhost:9000/bradypodion.js:339:32
    at Scope.$broadcast (http://localhost:9000/bower_components/angular/angular.js:12329:28)
    at $state.transition.resolved.then.$state.transition (http://localhost:9000/bower_components/angular-ui-router/release/angular-ui-router.js:1822:22) <bp-navbar class="ng-scope" role="navigation"> 
```

![screen shot 2014-03-15 at 20 57 18](https://f.cloud.github.com/assets/908242/2429349/0ec94fb6-ac7c-11e3-916f-1d21dd9ceae3.png)

Problem is that the [detected upState is not checked for existence](https://github.com/excellenteasy/bradypodion/blob/master/modules/scripts/directives/navbar.js#L129).