output: #fixed code
                                  public RpcData doHandle(RpcData data) throws Exception {
          
          Object input = null;
          Object[] param;
          Object ret;
          if (data.getData() != null && parseFromMethod != null) {
              input = parseFromMethod.invoke(getInputClass(), new ByteArrayInputStream(data.getData()));;
              param = new Object[] {input};
          } else {
              param = new Object[0];
          }
          
          RpcData retData = new RpcData();
          // process attachment
          if (getAttachmentHandler() != null) {
              byte[] responseAttachment = getAttachmentHandler().handleAttachement(data.getAttachment(), getServiceName(), getMethodName(), param);
              retData.setAttachment(responseAttachment);
          }
          
          ret = getMethod().invoke(getService(), param);
          
          if (ret == null) {
              return retData;
          }
          
          if (ret != null && ret instanceof GeneratedMessage) {
              byte[] response = ((GeneratedMessage) ret).toByteArray();
              retData.setData(response);
          }
          
          return retData;
      }
input: #vulnerable code 
                                  public RpcData doHandle(RpcData data) throws Exception {
          
          Object input = null;
          Object[] param;
          Object ret;
          if (data.getData() != null && parseFromMethod != null) {
              input = parseFromMethod.invoke(getInputClass(), new ByteArrayInputStream(data.getData()));;
              param = new Object[] {input};
          } else {
              param = new Object[0];
          }
          
          RpcData retData = new RpcData();
          // process attachment
          if (getAttachmentHandler() != null) {
              byte[] responseAttachment = getAttachmentHandler().handleAttachement(data.getAttachment(), getServiceName(), getMethodName(), param);
              retData.setAttachment(responseAttachment);
          }
          
          ret = getMethod().invoke(getService(), param);
          
          if (ret == null) {
              return retData;
          }
          
          if (ret != null && ret instanceof GeneratedMessage) {
              byte[] response = ((GeneratedMessage) input).toByteArray();
              retData.setData(response);
          }
          
          return retData;
      } 
                              #location 27 
                              #vulnerability type NULL_DEREFERENCE