File Juicer will report files which are completely empty. This message is only shown when File Juicer has searched the file entirely and found nothing but zeroed data inside. No recovery software will be able to extract anything from such a file.
Empty files can be created by other disk recovery tools which read a corrupted flash card or disk while reading the index of where a file should be. Because of the corruption the file is no longer there and only zeroed data is read.
To recover data in this case, you must go back to the original flash card or disk, and use a different recovery method, or perhaps a different flash card reader.