New Metadata not accessible through fast properties

[AaronLenoir]

// Open file that contains NO Vorbis Comment metadata block
using (FlacFile file = new FlacFile(Path.Combine("Data", "testfile5_temp.flac")))
{
        // Add new Vorbis Comment metadata block
	file.Metadata.Add(new VorbisComment());

        // VorbisComment should not be null
	Assert.IsNotNull(file.VorbisComment);
}