Fixed NPE in GameHelper.onConnectionFailed. #65

Null pointer exception occured in `GameHelper.onConeectionFailed`.

Fixed GameHelpers of BasicSamples and elipse_compat.

I think mActivity is the cause of NPE. But I could not say with
confidence. So I added a try-catch too.

I didn't modified EndlessTunnel's GameHelper. It uses the different
verion of GameHelper.