Java thin 3.0: DataStreamer partition awareness might break if assignment is not available at the moment

• ClientTable.getPartitionAssignment might return an empty list
• AbstractClientStreamerPartitionAwarenessProvider assumes that partition count can't change

Therefore, if some server node lags behind and returns an empty assignment for a given timestamp, streamer partition awareness won't work at all.

Potential Fixes

• Wait for assignment on the server, do not return empty/null - might affect performance
• Return correct partition count, but null values - faster and simpler