fix(CDNFile): Don't do file_exists check on 'getFullPath' if 'Filename' isn't set. (Avoids 'assets/' directory returning as an existing file)
fix(CDNFile): Don't do file_exists check on 'getFullPath' if 'Filename' isn't set. (Avoids 'assets/' directory returning as an existing file)

silverstripe-australia/silverstripe-cdncontent,silverstripe-australia/silverstripe-cdncontent