output: #fixed code
                                  @Override
      protected void process(ComplexEventChunk<StreamEvent> streamEventChunk, Processor nextProcessor, StreamEventCloner streamEventCloner) {
          while (streamEventChunk.hasNext()) {
              StreamEvent streamEvent = streamEventChunk.next();
              StreamEvent clonedEvent = streamEventCloner.copyStreamEvent(streamEvent);
              clonedEvent.setType(StreamEvent.Type.EXPIRED);
              if (count < length) {
                  count++;
                  this.expiredEventChunk.add(clonedEvent);
              } else {
                  StreamEvent firstEvent = this.expiredEventChunk.poll();
                  if(firstEvent!=null) {
                      streamEventChunk.insertBeforeCurrent(firstEvent);
                      this.expiredEventChunk.add(clonedEvent);
                  }
                  else {
                      streamEventChunk.insertBeforeCurrent(clonedEvent);
                  }
              }
          }
          nextProcessor.process(streamEventChunk);
      }
input: #vulnerable code 
                                  @Override
      protected void process(ComplexEventChunk<StreamEvent> streamEventChunk, Processor nextProcessor, StreamEventCloner streamEventCloner) {
          while (streamEventChunk.hasNext()) {
              StreamEvent streamEvent = streamEventChunk.next();
              StreamEvent clonedEvent = streamEventCloner.copyStreamEvent(streamEvent);
              clonedEvent.setType(StreamEvent.Type.EXPIRED);
              if (count < length) {
                  count++;
                  this.expiredEventChunk.add(clonedEvent);
              } else {
                  StreamEvent firstEvent = this.expiredEventChunk.poll();
                  streamEventChunk.insertBeforeCurrent(firstEvent);
                  this.expiredEventChunk.add(clonedEvent);
              }
          }
          nextProcessor.process(streamEventChunk);
      } 
                              #location 12 
                              #vulnerability type NULL_DEREFERENCE