Files get overwritten on upload

Hello,

I’ve noticed a bug that appears when I want to upload a file.
If I upload two images which have a same file name and upload them in same gallery, the second image will overwrite the first.

In the old version (1.9.5), it checks if there is a file with same name and then adds an index. In the latest version (2.0.27), it unfortunately does not work.

http://wordpress.org/plugins/nextgen-gallery/