Unhandled exceptions on Facebook login

[WheretIB]

FacebookOAuthException is not the only exception that might arise from LoginAsync call, please handle all exceptions internally here:

https://github.com/facebook-csharp-sdk/facebook-winclient-sdk/blob/master/Source/Facebook.Client/Session.cs#L513-L534

Note that because this is an async method, if the call to your library is not properly wrapped on the application side, this will lead to crash in UnhandledException handler.