title: Mvvmcross Location Plugin current and last seen locations are null
body: <p>I'm trying to get location in my application using mvvmcross location plugin, but it's always throw null reference exception because <code>CurrentLocation</code> and <code>LastSeenLocation</code> are always null. GPS service is enabled on real android device and permisions has been configured in android manifest. I've tested app on genymotion, and if I turn on GPS it works. I can't understand, why location provider doesn't provide location on real device.
  Here is code sample:</p>
  
  <pre><code> private void GetLocation()
      {
          IMvxLocationWatcher _locationWatcher = Mvx.Resolve&lt;IMvxLocationWatcher&gt;();
          _locationWatcher.Start(new MvxLocationOptions() {Accuracy = MvxLocationAccuracy.Fine}, OnLocation, OnError );
          try
          {
              Lat = _locationWatcher.CurrentLocation.Coordinates.Latitude;
              Lng = _locationWatcher.CurrentLocation.Coordinates.Longitude;
          }
          catch
          {
              Lat = _locationWatcher.LastSeenLocation.Coordinates.Longitude;
              Lng = _locationWatcher.LastSeenLocation.Coordinates.Longitude;
          }
      }
  </code></pre>