Synchronized processing the next RZNetworkUpload in the upload queue in RZClient. Added some more NSAsserts, fixed bug where RZClient/RZNetworkUpload would report errors when the output stream’s status wasn’t NSStreamStatusOpen. It is valid for the stream to be NSStreamStatusWriting and have space available at the same time. Fixed bug where trying to send ‘play’ to the clients when no clients are connected would crash.