#vulnerable code 
                              public void testUpdateOnSuccess() {
    // Set up
    TestHelper.resetDatabaseSync();

    Execution execution = new Execution(null, 12);
    execution.setEnd(2345);

    BasePage parent = new BasePage();
    ResultsPage page = new ResultsPage(parent);
    page.setMessageReceiver(new TabWrapper());
    page.setExecutionParameter("identifier", "name");

    page.startPolling(true);

    // Expected Values
    // Execute
    page.updateOnSuccess(null);

    // Check
    assertEquals(2, page.getWidgetCount());
    assertTrue(page.getWidget(1) instanceof TabLayoutPanel);
    assertEquals(2, ((TabLayoutPanel) page.getWidget(1)).getWidgetCount());

    // Cleanup
    TestHelper.resetDatabaseSync();
  } 
                            #location 17 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                              public void testUpdateOnSuccess() {
    // Set up
    TestHelper.resetDatabaseSync();

    Algorithm algorithm = new Algorithm("example_ind_algorithm.jar");
    Execution execution = new Execution(algorithm, 12);
    execution.setEnd(2345);

    BasePage parent = new BasePage();
    ResultsPage page = new ResultsPage(parent);
    page.setMessageReceiver(new TabWrapper());
    page.setExecutionParameter("identifier", "name");

    page.startPolling(true);

    // Expected Values
    // Execute
    page.updateOnSuccess(execution);

    // Check
    assertEquals(2, page.getWidgetCount());
    assertTrue(page.getWidget(1) instanceof TabLayoutPanel);
    assertEquals(2, ((TabLayoutPanel) page.getWidget(1)).getWidgetCount());

    // Cleanup
    TestHelper.resetDatabaseSync();
  }