Cannot write total tracks without track N in mp3

[Alex Novichkov]

Hi everyone!

I've stumbled upon a possible bug: When I tried to write TRCK frame
into id3v2.4 with the value "/5", that is with total tracks but
without track number, TagLib seemed not to understand this format,
though "1/" and "1/5" were written successfully. I used this code:

//TagLib::ID3v2::Tag *tag
    tag->removeFrames("TRCK");
    TagLib::ID3v2::TextIdentificationFrame *f = new
            TagLib::ID3v2::TextIdentificationFrame("TRCK");
    f->setText("0/2");
    tag->addFrame(f);

Is this really a bug or I've missed smth?