fix TrackerTest#testConsumerPrinter

app/src/main/java/org/astraea/app/performance/Performance.java

@@ -454,8 +454,6 @@ public void onPartitionAssigned(Set<TopicPartition> partitions) {
       nowPartitions = partitions;
       diffPartitions.retainAll(prevPartitions);
       stickyNumbers.put(clientId, diffPartitions.size());
-      System.out.println(clientId + " now assignment = " + nowPartitions);
-      System.out.println(clientId + " previous assignment = " + prevPartitions);
     }
 
     @Override

app/src/main/java/org/astraea/app/performance/TrackerThread.java

@@ -141,7 +141,8 @@ boolean tryToPrint(Duration duration) {
       for (var i = 0; i < reports.size(); ++i) {
         var report = reports.get(i);
         var ms = metrics.stream().filter(m -> m.clientId().equals(report.clientId())).findFirst();
-        var stickyNumber = Performance.RecordListener.stickyNumbers.get(report.clientId());
+        var clientId = report.clientId() == null ? "temp" : report.clientId();
+        var stickyNumber = Performance.RecordListener.stickyNumbers.get(clientId);
         if (ms.isPresent()) {
           System.out.printf(
               "  consumer[%d] has %d partitions and %d sticky partitions%n",