#vulnerable code 
                                public static long getWallClockTimeFromCellTimeStamp(long tsOfCell) {
        return TransactionFactory.getTransactionFactory().getTransactionContext().isPreExistingVersion(tsOfCell) ? tsOfCell : TransactionUtil.convertToMilliseconds(tsOfCell);
    } 
                            #location 2 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public static long getWallClockTimeFromCellTimeStamp(long tsOfCell) {
        return TransactionFactory.getTransactionProvider().getTransactionContext().isPreExistingVersion(tsOfCell) ? tsOfCell : TransactionUtil.convertToMilliseconds(tsOfCell);
    }