Zero-length files not accepted

[jcdr428]

When the .torrent includes zero-length files, these files are not included in the files list; the file list is not shown in the UI 'Files' tab; when unchecking files (i.e. file_priorites = 0), the wrong files are downloaded.

Empty files are not forbidden in the bittorrent specs.

Example of non-working .torrent:

d8:announce19:http://announce.com4:infod5:filesld6:lengthi0e4:pathl13:EmptyFile.txteed6:lengthi1000e4:pathl16:NonEmptyFile.txteee4:name11:TorrentFile12:piece lengthi16384e6:pieces20:ABCDEFGHIJKLMNOPQRST7:privatei0e6:source6:sourceee

[jcdr428]

My hint is this may come from sub_buffer being null or empty in 'metafile.py' line 359:

                if torrent_format.includes_v1():
                    a = piece_length - done
                    for sub_buffer in (buffer[:a], buffer[a:]):
                        if sub_buffer:
                            sh.update(sub_buffer)
                            done += len(sub_buffer)