fix potential null pointer access in Amazon GameCenter

It's possible that agsGameClient is initialized isReady() but the
callback, which loads lbClient and acClient, hasn't been called yet. That would
caush a null pointer access crash, because we only check the agsGameClient.
remove trailing spaces
Merge branch 'fix-amazon-gamecenter-nullptr' of https://github.com/michaelcontento/avalon into michaelcontento-fix-amazon-gamecenter-nullptr