In ezp 4.1.2 (and lower, I don't know exactly), ezFile::suffix returns complete filename when there is no extension, i.e. path/to/filename returns filename and path/to/filename.ext returns ext as expected.
This happens when browsing with webdav : some files have no extension and webdav has a buggy behaviour (http://issues.ez.no/IssueView.php?Id=15012&activeItem=2).

You can find a patch in attachment. We just return an empty string to satisfy condition at kernel/private/classes/webdav/ezwebdavcontentbackend.php:1520 "if( !$string )"