StackExchange/StackExchange.Redis — pull request #135 by deepakverma (2014-12-10 22:11:40+00:00)
Title: StackExchange.Redis to consider separately Response Array as either NULL  or an Empty Array

When multiple clients are trying to modify the same key in a transaction, Redis server returns null response *-1\r\n causing it to throw an “Unexpected response to EXEC: MultiBulk: 0” exception during transaction.ExecuteAsync()."
The fix is to consider *-1\r\n as a null array instead of empty array.