Avoid NPE in MultiNodePipelineBase (#3697)

Should get connection first and then create new pipeline queue, otherwise it would cause NPE when timeout for getting connection and call sync() method. If there is timeout for getting connection, the pipeline queue would be create for node, but connections map has no connection for this node. Once executing sync() method, it would throw NPE on connection.getMany() (line 112, connection is null)

Author: stillerrr

Diff for: src/main/java/redis/clients/jedis/MultiNodePipelineBase.java

@@ -63,16 +63,16 @@ protected final <T> Response<T> appendCommand(CommandObject<T> commandObject) {
       queue = pipelinedResponses.get(nodeKey);
       connection = connections.get(nodeKey);
     } else {
-      pipelinedResponses.putIfAbsent(nodeKey, new LinkedList<>());
-      queue = pipelinedResponses.get(nodeKey);
-
       Connection newOne = getConnection(nodeKey);
       connections.putIfAbsent(nodeKey, newOne);
       connection = connections.get(nodeKey);
       if (connection != newOne) {
         log.debug("Duplicate connection to {}, closing it.", nodeKey);
         IOUtils.closeQuietly(newOne);
       }
+
+      pipelinedResponses.putIfAbsent(nodeKey, new LinkedList<>());
+      queue = pipelinedResponses.get(nodeKey);
     }
 
     connection.sendCommand(commandObject.getArguments());