don't assume bytebuffer limit is set

processing/src/main/java/io/druid/query/aggregation/hyperloglog/HyperUniquesBufferAggregator.java

@@ -66,9 +66,11 @@ public class HyperUniquesBufferAggregator implements BufferAggregator
   @Override
   public Object get(ByteBuffer buf, int position)
   {
-    ByteBuffer dataCopyBuffer = ByteBuffer.allocateDirect(HyperLogLogCollector.getLatestNumBytesForDenseStorage());
+    final int size = HyperLogLogCollector.getLatestNumBytesForDenseStorage();
+    ByteBuffer dataCopyBuffer = ByteBuffer.allocateDirect(size);
     ByteBuffer mutationBuffer = buf.duplicate();
     mutationBuffer.position(position);
+    mutationBuffer.limit(position + size);
     dataCopyBuffer.put(mutationBuffer);
     dataCopyBuffer.rewind();
     return HyperLogLogCollector.makeCollector(dataCopyBuffer);