NPE when issuing multi-exec against cluster

[rovarghe]

Test case: (4.1.Final)

        RedisClusterClient rcc = RedisClusterClient.create(uris);
        cconn = rcc.connect();
        RedisAdvancedClusterCommands ccommands = cconn.sync();

        ccommands.multi();

        ccommands.set("one", "1");
        ccommands.set("two", "2");
        ccommands.mget("one", "two");
        ccommands.lpush("list", "11");
        ccommands.llen("list");

        ccommands.exec();

Throws:
java.lang.NullPointerException
at com.lambdaworks.redis.cluster.ClusterDistributionChannelWriter.write(ClusterDistributionChannelWriter.java:99)
at com.lambdaworks.redis.RedisChannelHandler.dispatch(RedisChannelHandler.java:106)
at com.lambdaworks.redis.cluster.StatefulRedisClusterConnectionImpl.dispatch(StatefulRedisClusterConnectionImpl.java:189)
at com.lambdaworks.redis.AbstractRedisAsyncCommands.dispatch(AbstractRedisAsyncCommands.java:1726)
at com.lambdaworks.redis.AbstractRedisAsyncCommands.dispatch(AbstractRedisAsyncCommands.java:1721)
at com.lambdaworks.redis.AbstractRedisAsyncCommands.dispatch(AbstractRedisAsyncCommands.java:1717)
at com.lambdaworks.redis.AbstractRedisAsyncCommands.exec(AbstractRedisAsyncCommands.java:351)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.lambdaworks.redis.cluster.StatefulRedisClusterConnectionImpl$ClusterFutureSyncInvocationHandler.handleInvocation(StatefulRedisClusterConnectionImpl.java:334)
at com.google.common.reflect.AbstractInvocationHandler.invoke(AbstractInvocationHandler.java:87)
at com.sun.proxy.$Proxy4.exec(Unknown Source)

[mp911de]

Fixed NPE but this won't fix the problem of transaction coordination. I posted my considerations about Redis Cluster Transactions as they could be seen from a high-level API to https://www.reddit.com/r/redis/comments/445u9e/redis_cluster_transactions/