output: #fixed code
                                  @Test
      public void getMemoryTxs() throws Exception {
  
          assertNotNull(service);
  
          Transaction tx = new TestTransaction();
          tx.setTime(0l);
  
          assertEquals(tx.getHash().getDigestHex(), "0020c7f397ae78f2c1d12b3edc916e8112bcac576a98444c4c26034c207c9a7ad281");
  
          Result result = service.newTx(tx);
          assertNotNull(result);
          assertTrue(result.isSuccess());
          assertFalse(result.isFailed());
  
          List<Transaction> memoryTxs = service.getMemoryTxs();
          assertNotNull(memoryTxs);
  
          assertEquals(1, memoryTxs.size());
  
          tx = memoryTxs.get(0);
          assertNotNull(tx);
          assertEquals(tx.getHash().getDigestHex(), "0020c7f397ae78f2c1d12b3edc916e8112bcac576a98444c4c26034c207c9a7ad281");
      }
input: #vulnerable code 
                                  @Test
      public void getMemoryTxs() throws Exception {
  
          assertNotNull(service);
  
          Transaction tx = new TestTransaction();
          tx.setTime(0l);
  
          assertEquals(tx.getHash().getDigestHex(), "08001220d194faf5b314f54c3a299ca9ea086f3f8856c75dc44a1e0c43bcc4d80b47909c");
  
          Result result = service.newTx(tx);
          assertNotNull(result);
          assertTrue(result.isSuccess());
          assertFalse(result.isFailed());
  
          List<Transaction> memoryTxs = service.getMemoryTxs();
          assertNotNull(memoryTxs);
  
          assertEquals(1, memoryTxs.size());
  
          tx = memoryTxs.get(0);
          assertNotNull(tx);
          assertEquals(tx.getHash().getDigestHex(), "08001220d194faf5b314f54c3a299ca9ea086f3f8856c75dc44a1e0c43bcc4d80b47909c");
      } 
                              #location 9 
                              #vulnerability type NULL_DEREFERENCE