No connectivity exception (moved from facebook-csharp-sdk)

[sanjeevdwivedi]

facebook-csharp-sdk/facebook-csharp-sdk#280

The SDK seems to raise an exception if there is no internet connectivity. In the tutorial we are instructed to create an instance of FacebookSessionClient straight away in the app.xaml.cs without checking connectivity. So when I test on an winphone8 emulator, the following exception is raised several seconds after startup:

{Facebook.WebExceptionWrapper: The remote server returned an error: NotFound. ---> System.Net.WebException: The remote server returned an error: NotFound.
at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClasse.b__d(Object sendState)
at System.Net.Browser.AsyncHelper.<>c__DisplayClass1.b__0(Object sendState)
--- End of inner exception stack trace ---
at System.ComponentModel.AsyncCompletedEventArgs.RaiseExceptionIfNecessary()
at Facebook.OpenReadCompletedEventArgs.get_Result()
at Facebook.Client.FacebookSessionClient.b__0(Object o, OpenReadCompletedEventArgs e)
at Facebook.HttpHelper.OnOpenReadCompleted(OpenReadCompletedEventArgs args)
at Facebook.HttpHelper.ResponseCallback(IAsyncResult asyncResult, Object userToken)
at Facebook.HttpHelper.<>c__DisplayClass2.b__0(IAsyncResult ar)
at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClass1d.b__1b(Object state2)}

//cc @RamsayGit