I don't think its anything to be concerned about. I'm ignoring the wordfence error for now. Even though I'm not a coder, I've looked over the file and think its OK. Tho it be good if you could use another method or work with wordfence so the code is not flagged. I didn't get this issue with the previous version just the new version after updating.
Tho it be good if you could review your code so it doesn't get flagged by WordFence as a potential issue.
Word fence error:
This file may contain malicious executable wp-content/plugins/nextgen-gallery/products/photocrati_nextgen/modules/datamapper/class.datamapper_driver_base.php
File type: Not a core, theme or plugin file.
Issue first detected: 1 day 21 hours ago.
Status Ignoring this file until it changes
This file is a PHP executable file and contains the word 'eval' (without quotes) and the word 'base64_decode(' (without quotes). The eval() function along with an encoding function like the one mentioned are commonly used by hackers to hide their code. If you know about this file you can choose to ignore it to exclude it from future scans.