#vulnerable code 
                                @Override
    void assertExpectedReadQueryDistribution( Context context )
    {
        Map<String,Long> readQueriesByServer = context.getReadQueriesByServer();
        ClusterAddresses clusterAddresses = fetchClusterAddresses( driver );

        // before 3.2.0 only read replicas serve reads
        ServerVersion version = ServerVersion.version( driver );
        boolean readsOnFollowersEnabled = READ_ON_FOLLOWERS_BY_DEFAULT.availableIn( version );

        if ( readsOnFollowersEnabled )
        {
            // expect all followers to serve more than zero read queries
            assertAllAddressesServedReadQueries( "Follower", clusterAddresses.followers, readQueriesByServer );
        }

        // expect all read replicas to serve more than zero read queries
        assertAllAddressesServedReadQueries( "Read replica", clusterAddresses.readReplicas, readQueriesByServer );

        if ( readsOnFollowersEnabled )
        {
            // expect all followers to serve same order of magnitude read queries
            assertAllAddressesServedSimilarAmountOfReadQueries( "Followers", clusterAddresses.followers,
                    readQueriesByServer, clusterAddresses );
        }

        // expect all read replicas to serve same order of magnitude read queries
        assertAllAddressesServedSimilarAmountOfReadQueries( "Read replicas", clusterAddresses.readReplicas,
                readQueriesByServer, clusterAddresses );
    } 
                            #location 9 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    void assertExpectedReadQueryDistribution( Context context )
    {
        Map<String,Long> readQueriesByServer = context.getReadQueriesByServer();
        ClusterAddresses clusterAddresses = fetchClusterAddresses( driver );

        // expect all followers to serve more than zero read queries
        assertAllAddressesServedReadQueries( "Follower", clusterAddresses.followers, readQueriesByServer );

        // expect all read replicas to serve more than zero read queries
        assertAllAddressesServedReadQueries( "Read replica", clusterAddresses.readReplicas, readQueriesByServer );

        // expect all followers to serve same order of magnitude read queries
        assertAllAddressesServedSimilarAmountOfReadQueries( "Followers", clusterAddresses.followers,
                readQueriesByServer, clusterAddresses );

        // expect all read replicas to serve same order of magnitude read queries
        assertAllAddressesServedSimilarAmountOfReadQueries( "Read replicas", clusterAddresses.readReplicas,
                readQueriesByServer, clusterAddresses );
    }